24 weeks

Hi. I experienced recently having diarrhea without any reason. I went to my OB and had some laboratory test and the result was negative. I was just worried that for this month of april every weekend im having diarrhea. Then yesterday morning i was just walking on the mall and experienced stomach cramp and went home to had my poo and it was twice. Unfortunately it happened again today . :(

Can anyone tell me whats wrong? Should i have a second opinion?