Its all about "SEX".........?

I'm 17 he's 21 my mum and his mum bestfriends & there cool with us dating, known him since I was 6 so almost half my life ;L, he said when I was 14? We had to wait till I was older so it wouldn't be weird. Well I'm 17.. We always make out at night and obv we can't have sex I'm underage but we always keep trying but we always stop before it gets into actully "sex" but I can't be arsed stopping it's my sexual feelings making me just pounce on him.... :/ help