My penis curves when I'm hard. Why does it curve?
Slight curves are normal. There are three chambers in your penis: two on top and one on the bottom. When you have an erection, those chambers fill up with blood, much like blowing up a balloon with air. If you have ever blown up a long balloon, you will notice that they are rarely perfectly straight. There is almost always a slight curve. That is because the surface of the balloon is not perfectly even. Well, guess what? The chambers in your penis are not perfectly even either. Three of them balances each other out, but still there will be a slight curve.