What should i do!?( i need relationship advice )?

ok so here it is, theres 2 girls, one of them iv been dating for about a month, its pretty much all about sex, im a guy, but thats not all i want, i have a consious, and using a girl for sex isent quite making me feel great, now this other girl, i really like, but they both come from completly different backrounds, both use drugs, but the one im with has family in jail, her moms been in and out of jail her whole life, her bro is on crack and whatever else he can get his hands on, hes been in jail most of his life, unfortunattly hes not right now. he told me if i broke his sister heart hed break my neck, and that murders just another charge. im only 16, this stuffs pretty messed up. however i really like this other girl, i just want a fresh start, but i just dont know what to do. i also have been locked up for 10 months of my life, no violent crimes, just drug dealing and such, i can easly get my hand on a semi auto/ fully auto peice...but i just dont want to have to worry about this. i want a new life, but what is a kid to do if hes going to be fearing for his life? please help me...i need to know what to do...any answers help