Some colleges do have psychiatrists on staff. And it can be helpful having contact with a therapist or MD at the school for communication with deans and professors concerning accommodations and so on. Then again some prefer privacy and seek help outside of the school.
Antidepressants can be prescribed, even for bipolar 1 patients, but for bp1 they must be on a mood stabilizer first.
If the original poster is using “mania” loosely, that is another thing. Mania has very specific elements and is not all that hard to diagnose. Hypomania is a little murkier.
Clearly the main issue here isn’t how to avoid parents finding out, but how to talk to the parents about difficulties and get any needed help. It is possible that a therapist could help with this. I am sorry it is so scary to think of your parents discovering you are struggling.