You might want to try a different formula.
We had this problem for a short time and I did several things:
I did give prune water (soaked prunes in boiled water and gave the water cooled), but you will find mane mommies who think it's way too early to do that.
I also used caraway seeds oil, massaging the belly in circles.
And the best thing that helped us was bicycle movement with the legs - so simple and it worked like magic!
If it does continue I think you should go see the Dr. though, just to be on the safe side.