Hi I have never used herion in my life I went to the dr and my drug test came up positive for herion I left my boyfriend in May and in June there was a little in my system and then he can to see me the last weekend of June and I went to the dr on July 17 we had a lot of sex and the dr said that I tested positive for herion but there was a lot more in my system than the last time how is it possible if I have never ever done herion or been around it but my boyfriend has done it and I think he has done it a lot?