What Causes Fishy Smell From The Penis?

hello i am very frustrated because having sex with my boyfriend unprotected seems to be an issue. since we have been together i have had bacterial vaginosis 3 times and also 2 cases of yeast infections. after taking medication for the BV i decided we should use a condom and for a few months i went BV free but recently we had unprotected sex and now i am going through another yeast infection. i feel that it's because he is uncircumcised because sometimes he has a very strong smell around his penis. it is a fishy smell sometimes it is too strong. my doctor wanted to give him treatment but i dont know how this will help the smell. please give me advice on what you think is happening