how do i know if my boyfriend is addicted ?

About a month ago i found out that my boyfriend had tried marijuana while drunk with some mates, when i confronted him about it he said that he only took one draw and said that he would never do it again. So i thought everything was fine until I called one of my friends who he gets drunk with and he said that my boyfriend had had a whole splif and i felt so betryed and annoyed at him. When i was with him one day i smelt something funny and asked him what it was and he told me it would be the smoke from the weed, he said it smelt so good and i was worried because to me it made me want to puke everywhere and one day my friend said that he looked every weird and asked him if he needed a fag or if he had had on that day (as he also smokes) and he looked at he and said not yet...maybe thats why im all fidgity, i just get worried, as anyone would be, i don't know what he does with our group of mates, as i don't like to be around them when they drink, i only have what im told by them to see what he does at nights and when he's out. I don't know if he still smokes it as he hasnt been out in a while but we have been on seperate holidays for about 3 weeks and I am too scared to ask him if he is still taking it, and i was just wondering if anyone can give me any signs to look out for to see if he is still taking it or even addicted ?
thanks.