Is He Using?

My Boyfriend of 4years has changed i know he used a year or two ago, and stopped. But now i find little bottle caps of water sitting around his pupils are pinpoints he says his sick , but when i ask he says no. Why would you think that? he says i know when he did it before he sniffed it, but now i think he's shooting up i dont know he doesnt have track marks on his arms should i just buy a at home drug test?