Text rendering not working correctly

Question

so I'm trying to render some text using FTGL, GLFW and GLEW libraries in my C++ engine following this tutorial: https://www.youtube.com/watch?v=Rsdc6I80aFQ. But when I do so where the text should be instead of characters I get triangles of some kind (screenshot):

I wanted to use the same shader as when I'm rendering normal sprites, so I set the model matrix in shader to identity matrix and instead I'm passing character positions to the shader with VBO.

Here's font class:

class Font
{
private:
    /* Variables */
    ftgl::texture_atlas_t* m_atlas;
    ftgl::texture_font_t* m_font;

public:
    /* Constructors */
    Font(const char* filename, const float size)
        : m_atlas(ftgl::texture_atlas_new(512, 512, 1)),
          m_font(ftgl::texture_font_new_from_file(m_atlas, size, filename))
    {}

    /* Functions */
    void bindFontTexture() const
    {
        GLcall( glBindTexture(GL_TEXTURE_2D, m_atlas->id) );
    }

    // Getters
    inline ftgl::texture_font_t* getFTGLFont() const { return m_font; }

};

And here is label class (labels are 2D renderables with some text in my engine):

class Label2D : public Renderable2D
{
protected:
    /* Variables */
    std::string m_text;
    Color m_color;
    Font* m_font;

public:
    /* Constructors */
    Label2D(const std::string& text, const vector2& pos, const vector2& size, Font* font)
        : Renderable2D(pos, size), m_text(text), m_font(font)
    {}
    Label2D(const std::string& text, const vector2& pos, const vector2& size, Font* font, const Color& color)
        : Renderable2D(pos, size), m_text(text), m_font(font), m_color(color)
    {}

    /* Functions */
    void bindFontTexture() const
    {
        m_font->bindFontTexture();
    }

    // Setters
    void setText(const std::string& text)
    {
        m_text = text;
    }
    void setColor(const Color& color)
    {
        m_color = color;
    }
    void setFont(Font* font)
    {
        m_font = font;
    }

    // Getters
    inline const std::string& getText()  const { return m_text;  }
    inline const Color&       getColor() const { return m_color; }

    inline ftgl::texture_font_t* getFTGLFont() const { return m_font->getFTGLFont(); }

};

Here's my text rendering code. Now I DO know this code is written terribly since I shouldn't create a VAO and VBO everytime I want to render some text, but I did it only for test purposes, I just want to be sure that library is working fine, then I will organize the code:

void Layer2D::m_renderLabels(const bool renderLighting)
{
    // Uniforms Setup
    m_textureShader.start();

    m_textureShader.setUniformMatrix4f("u_modelMatrix", matrix4(1.0f));f));

    // Rendering Labels from std::vector
    for (Label2D* label : m_labels)
    {
        // Binding
        m_textureVAO.bind();

        label->bindFontTexture();

        // Starting Shader
        m_textureShader.start();

        // Preparation Stuff
        std::vector<float> positions;
        std::vector<float> textureCoordinates;

        float offsetX = label->getPosition().x;

        // Loading Characters
        for (unsigned int i = 0; i < label->getText().length(); i++)
        {
            // Loading Glyph
            ftgl::texture_glyph_t* glyph = ftgl::texture_font_get_glyph(label->getFTGLFont(), &label->getText().at(i));

            if (glyph != NULL)
            {
                if (i > 0)
                {
                    float kerning = texture_glyph_get_kerning(glyph, &label->getText().at(i - 1));
                    offsetX += kerning;
                }

                // Glyph Position/Offset/Size Calculations
                float x0 = offsetX + glyph->offset_x;
                float y0 = label->getPosition().y + glyph->offset_y;
                float x1 = x0 + glyph->width;
                float y1 = y0 - glyph->height;
                float u0 = glyph->s0;
                float v0 = glyph->t0;
                float u1 = glyph->s1;
                float v1 = glyph->t1;

                positions.push_back(x0);
                positions.push_back(y0);
                positions.push_back(x0);
                positions.push_back(y1);
                positions.push_back(x1);
                positions.push_back(y1);
                positions.push_back(x1);
                positions.push_back(y0);

                textureCoordinates.push_back(u0);
                textureCoordinates.push_back(v0);
                textureCoordinates.push_back(u0);
                textureCoordinates.push_back(v1);
                textureCoordinates.push_back(u1);
                textureCoordinates.push_back(v1);
                textureCoordinates.push_back(u1);
                textureCoordinates.push_back(v0);

                offsetX += glyph->advance_x;
            }
        }

        VertexArray textVAO;
        VertexBuffer* textPosVBO = new VertexBuffer(&positions[0], positions.size(), 2);
        VertexBuffer* textTexCoordsVBO = new VertexBuffer(&textureCoordinates[0], textureCoordinates.size(), 2);
        textVAO.addAttribute(textPosVBO, 0);
        textVAO.addAttribute(textTexCoordsVBO, 1);
        textVAO.bind();

        // Rendering
        GLcall( glDrawArrays(GL_TRIANGLE_STRIP, 0, 4 * label->getText().length()) );

    }
}

And lastly that's the shader code: Vertex:

#shader vertex
#version 330 core


layout(location = 0) in vec2 in_position;
layout(location = 1) in vec2 in_textureCoordinates;


out vec2 pass_textureCoordinates;


uniform mat4 u_projectionMatrix;
uniform mat4 u_viewMatrix;
uniform mat4 u_modelMatrix;


void main()
{
    pass_textureCoordinates = in_textureCoordinates;

    gl_Position = u_projectionMatrix * u_viewMatrix * u_modelMatrix * vec4(in_position, 0.0, 1.0);
}

And fragment:

#shader fragment
#version 330 core


in vec2 pass_textureCoordinates;


out vec4 out_color;


uniform sampler2D u_textureSampler;


void main()
{
    vec4 textureColor = texture2D(u_textureSampler, pass_textureCoordinates);

    out_color = textureColor;
    out_color = vec4(1.0, 0.0, 0.0, 1.0); //done for test purposes only (it still doesn't work when this line is removed)
}

I'm sorry if I wasn't specific enough, if I could provide any more information to help You help me, just please comment down below.

Thanks in advance!

EDIT: If You were wondering, I do set projection and view matrices in other parts of code:

m_textureShader.start();
m_textureShader.setUniformMatrix4f("u_projectionMatrix", m_projectionMatrix);
m_textureShader.setUniformMatrix4f("u_viewMatrix", viewMatrix);

EDIT: After swapping the last 2 vertices I get quads now, but still not a text (screenshot) The quads aren't red because I removed the debugging line from fragment shader.