Boyfriend trouble , advice please ?

My "boyfriend"(he will be M) and I (never became official but he's called me his girlfriend before) are happy , for the most part . One flaw , he does drugs . Coke , shrooms , salts , all kinds . I told M i don't want him to do drugs at all except weed bc idgaf about a little green every now & then . he basically ignored me and changed the subject . i actually think one time he said "good luck getting that to happen" . Also , he keeps getting mad because i don't like his nasty ex that keeps trying to get with him and talks trash on me daily . 

I was visiting my family in a town over this week and i met some people , one of them i bonded with quickly and we got close (let's say N) . i met them sunday . on monday when he drove me to my family's house , N kissed me and it honestly made me so happy . every time i'm around him i feel so good . my heart flutters when he texts me and my skin tingles when he touches me . but i love M . i feel so much for N and i know it's wrong , i feel guilty too , but i feel things i don't feel for M and it scares me . Any advice ? (told you it'd be long)