I have an IQ of 127, OK? University was nearly my undoing. I would have eventually washed out if I hadn't have dropped out. Unbeknownst to me, I had depression at the time.
School is hard enough as it is without stuff like mental illness. It's designed to weed out the people who mess around and party all the time. But if you have a mental illness, it can be really hard or if you're not ready for the 4 year commitment.
You are not stupid! You were bright enough to make it into college, nowadays that's no mean feat. You're just feeling the pressure.
You might want to go to the counselling services on campus and talk to them about it, see what they have to say.
YOU ARE NOT STUPID!!!!!