I also think that you need to just clean out your belly button it is a hole and like anything else stuff gets stuck in it you can use alcohol i always lay dwon and pour a little bit of baby oil in there let it sit for about a minute then use a qtip to clean it and then alcohol to make it extra clean!!
I have an obnoxiously deep bellybutton. In fact, it's at least 2 inches deep. As such, it always gets smelly just from sweat and dead skin cells. My belly button is also very narrow and tender. If I try to pour anything caustic in it like rubbing alcohol or even some soaps, it burns unbelievably. I thought I'd never be able to be my belly button to stop smelling until I discovered that stuffing it with baking soda, letting it sit for a few minutes, and then washing it out using a Q tip did just the trick. It was amazing how it didn't smell at all! If you have smelly belly button problems and you don't think it's an infection, I highly recommend trying baking soda!