My boyfriend's private parts sometimes smell like he has been with a girl, at times he has not been with me! I wonder, are there other things than cheating that could make him smell that way (like something he might eat)?

Well, ask him about it. Try being subtle at first. Just ask a few questions, like does he wear perfume or colone. Sometimes I will put perfume on 'there' to  smeall pretty for my husband.
Or ask him what he eats for food. If he has eaten anything unusual then its a possiblity.
Maybe its his soap? Some soaps have a very perfumey, sweet smell.
Try this. Ask him what type of soap he uses. Then go to the store and buy that soap. Open it up and smell it. If it smells the same, then that's your answer. If not, then I suspect your right. But ask him about it BEFORE you break up with him. Otherwise you could be looking mighty foolish

As well, if he has been perspiring (due to heat, humidity or exertion) the smell can be quite similar to that of female odor, just usually less strong. Also, if he has not been cleaning himself as well as he should, the same smell can result. As mentioned by others, have him keep himself clean, and you shouldn't have any more problems.

Don't waste time and energy worrying if he's cheating. If its going to happen, it will happen. Tell him to shower and wash his junk before macing down on him and you wont have to deal with the smell .

Oh that's nothing. He just need to take a shower---- soap with germ protection, body shampoo, hair shampoo and conditioner and skin cleanser. Buy him some perfumes, body spray, deodorants, hair oil, body lotion  and everything you can get hold of!