Yesterday i found a syringe in my boyfriend's drawyer..?

me and me bf have been together for 2 years and 4 months and were havign a baby boy.. i know he wouldnt do these things bcs we're having something big .. i know he takes weed as he works in holland too and i dont blame him he's works on an oil rig its not easy.. anyway while he was getting washed i looked in his drawer and i saw the syringe..when i confronted him he got mad saying he bought it on purpose to see if i would acually look.. and called me nosy and stuff..i had seen him hiding something.. and i looked :( and he said he bought it on purpose to see..but i doubt it..i remember his left arm hurting a lot and stuff..and before getting washed he went and took something else from the drawyer he just wouldnt tell me though :( please help.. there was also a bag there with a code kind of (f- and some numbers i think ).. can anyone explain this? i need to know if he is lying or not ..i dont know what to think but im sure he didnt tell me the truth cos he knows he would loose me :(