Should I?

I just got out of a very abusive relationship (physically, mentally, and emotionally) that I was in for 5 years. He cheated on me 3 times but i stayed. I finally had enough courage to leave him after a bad altercation. But I met a really sweet guy online that we just want to be fuck buddy's. (I've never had sex with anyone else other than ex). My ex found out and now is trying to convince me not to sleep with this guy because it wouldn't be fair and I'll be "Damaged goods" that he wont want if we get back together in the future. Should I not do it or should I just say fuck it and have some fun and experience life?? (I'm 18 btw)