How can I tell if he's still using

[Baggins]

I have a problem with my boyfriend. He smokes pot which I've always known about and could really care less about. The problem is before we got together we used cocaine and was dealing. When we got together I told him what he did in the past stayed in the past. My problem now is I found coke in his pocket, there was even a little still in the bag and I confronted him and we had this big fight I even made him cut all his fingernails and I made him promise to never do it again yet I'm still very suspicious. I just need to know what other signs to look for and places to search.