I made a deal with my Mom and Dad. They agreed to fund my med school as long as I took it seriously, made passing grades and grew up. At $45,000 a year I thought that was a fair offer. I set my limits to two beers or one glass of wine at parties and have stuck with it for four years. Right now I have a 3.95 average and never felt better about myself. I have counted 37 that entered school along with me that are no longer here because of drinking, partying and drugging. Glad I am not one of them.
My suggestion would be to stay in the library until they longer miss you. Find new friends. Good luck
Find other friends, but keep in touch with your current friends too. Maybe go out with them just once in a while, and talk to them.