Just sharing this because i feel like it, maybe someone else here might experience something similar.
Its something like im aggravating my natural umbilical hernia (your belly button) from heavy weight training.
It will seem to come and go in cycles. For a few weeks/month i wont have anything, then i will gradually get an odd tingling stinging type of sensation in/around the navel. Then after a while it will be accompanied by a little bulge right beside the navel a little smaller than the size of a penny.
I will then cut back on heavy stuff, do more fast/explosive stuff, after a couple weeks i will be back to normal again.
I postulate that minor abdominal things like this are more prevalent with relative large torso individuals such as myself. More surface area, MORE PLACES TO RIP YOUR GUTS OPEN.
Other than this i feel quite good.