first of all disable in every rendering instead set it after resizing window (resize gl window procedure)
Setting projection matrices in every frame is peanuts for the GPU.
I usually do so, because there can be a lot of post processes, HUDs etc.
Things that can hurt performance:
1. No graphics driver installed. Sounds trivial, but I run into the problem. I was disappointed how slow openGL is. Then i realized something is wrong with the driver, i updated it and bam! at least 200 times faster rendering (it was really about 200).
2. You use non power-of-too textures.
3. Other stuff... Maybe for some reason, your openGL switches to "software rendering" instead of hardware rendering. Try to google that, I don't know specifics about why this can happen.