Advise anyone??..

So I've been dating my boyfriend for 10 months Tuesday and he's been asking me to give him a blow job for the past couple of months but I'm to scared to do it... The main reason why is because he's played me quiet a few times and every time we've "done more" he's played me... Like after the first time he fingered me I found out he was talking to like 3-4 other girls and we were already dating for like 4 months.. He knows I'm to scared to do it because of trust issues but he keeps promising he's not gonna do that anymore... My friends keep telling me do it then he won't play me anymore but I wouldn't want him to play me either way.. Please be kind.. I've never asked on here before...