Okie so is it grades that is worrying you? Is this your first semester in US? are you undergrad or grad student? Are you research assistant or teaching assistant? I know i am asking you too much question, but i am only trying to help.

Let me tell yo one thing, it is actually very common whatever you are experiencing. We all go through these phases in life. You are putting too much pressure in yourself. Believe me brother you will be fine. It might be kind of cultural shock, homesickness and over the top expectation.

You said studies is bothering you. I wish you could be more specific. Is it a particular subject or is it overall? is it particular test that you bombed or a particular project where you think it is deadend.

I would not worry about eating and sleeping alot since you are young. But it is better to zoom in to the thing that is bothering you.

If this is ya first semester you still have lot of time in your hand until finals. So you should not worry. Just stay focus without worrying too much. If you worry about consequences too much it will really start to bother you. It will induce panic attacks.
 
Right now you are suffering from some form of anxiety. But don't let it overwhelm you. Also keep check on your caffeine intake.

During these period you will have heightened vigilance. As much as possible never go down with a thought that starts with "what if." Talking to friends and family will also help keeping this feeling away.