Badly need advice!!

I'm 16 and I've always wanted to lose my virginity to a close friend rather than a boyfriend. 
Recently I've started getting close with a boy who's 19 and who tells me he really likes me and after meeting a few times and kissing quite a lot he wants to "step things up" 
I feel ready for this and I do like him I just feel like I'll be seen as a slut if I sleep with him because despite being close, we've only met a few times.
I'm worried I'll lose him as a friend no matter what I decide to do.
Someone please help??