Is it normal that my belly button smells bad >?

i'm just amazed you got your nose into it

Worse than your ASS?

Well, it's not normal that it smells bad. You must have an "innie" I imagine?
Well, some BB's are pretty deep and bacteria sits in there due to moisture from the shower, soap not rinsed completely, sweat, lint and skin cells. This all combined sitting in a dark warm place?

Yup, a rank smell indeed.

Here's what I would do: First I would lay on my back and pour in Peroxide and let that sizzle for a few minutes. Turn so it comes out, cotton ball area and swab it dry inside. (GENTLY!) Then with a NEW cotton swab (Q-tip) I would (while using other hand to try to open BB as much as possible) GENTLY clean out BB again using Baby oil or Witch Hazel on the q-tip.

After that..just get into the routine (Once it IS clean) after you get out of the shower/bath each day, towel dry your body, then take a q-tip and gently put it into the BB so the cotton sucks up the water. Every couple days you can do the Baby oil swipe w/q-tip. (haha..Do the "Baby Oil Swipe"..sounds like a dance! lol)

But really, you don't want things getting worse.

Drop a bit of tee tree oil
In there, problem solved. It stops fungal infection

How do you smell your bellybutton?

Wash it then.