Yes, it COULD be the gallstones! I had the same problem for years and I didn't know what it was. But, one month after my second labor I got diarrhoea for two months, I went to the ultrasound and they found a lot of small gallstones. Two weeks after that I had the first serious gallbladder attack (once you had it, you will know exactly what it is). I recommand you to go to the ultrasound of your abdomen and you will know.