I can't sleep sometimes due to past memories keep repeating in my head, or fear of the past will happen again with something/someone with what is going on, etc...

The last time this happened (last week), me grabbing my bear and it helped.. Sometimes just a simple thing like that can help, and I really don't care if people think- "Beauflow your an adult, you should not have a stuffed animal with you while you sleep--" I don't care!.... my cat some times sleeps with me which can help-
Another thing also is -- Do A Quiet activity for a little bit IF you can (I have failed at this but also it has helped too at times) to get your mind off of what you are thinking of...
Sometimes with me writting out what is bothering me can help-- BUt That does not work fro everyone.

I agree you should talk to someone either at the college you will be at, or finding someone on the side...

Reading that you can not talk to people with in your family, I think for you to talk to Someone will help-- As the others have said you don't have to do this alone, you can get better,

Best wishes to you and many hugs....