Wonder if its something you are eating/drinking the night before , try not snacking after dinner .or drinking much other than water.
I had something like this for 17 months, lost 17 kgs during that time, and became anemic. Then I found out that I had a parasite which is usually found mostly in children...I am neither a kid, nor do I have one.
The parasites love sugar and starches, but hate garlic, fibre, cayenne pepper, pineapples and pomegranate juice.
If you are willing to test yourself, I suggest you go and buy some cayenne pepper capsules. take 1 during each meal, and check your poop for three days...after that they usually come out and you see them.
If the pain gets really burny though, you might have an ulcer somewhere.
Else, it usually helps to eat sugar and starch free for a while, to stay sane.
Good luck!