There are tons of ways of doing things if you live with your parents. Think of reasons you CAN fuck girls, not excuses why you can't. Sure, it's more difficult, but here are numerous observations:
Ask yourself: are your parents going to actually stop you bringing a girl to your house? Or is it just the sex part you're worried about? In any case, my parents are devout Mormons and I've had plenty of girls over. If your parents want to meet her, just give them a short introduction when she comes over, and then ideally your parents go to another room. When I want to get down to business, just walk the girl to your room and close the door. If you think your mom or dad is literally going to barge in your room then we'll have to think of a different solution.
Maybe you're worried about the girl thinking you're a loser for living with your parents? Girls who like you or find you attractive will not give a shit. Especially college girls at your age. It's totally normal.
Scotty from GLL routinely brought girls to his parents' house for one night stands.
In the case that your parents are insanely strict or will barge into your room if they think you're having sex, you could potentially sneak the girl in, maybe while your parents are sleeping or something. I had a girl offer to sneak in my window once (wasn't necessary though).
Otherwise, if it is not humanly possible for you to have a female in your room while living with your parents, and she doesn't have any place she can bring you either, you can also have sex with girls in your car. Girls who want to have sex with you will do it.
Hope this helps.