IBS??

Tasha
Ok this may be tmi... But.... Question.. 
Should I be worried that for 3 months now every single time I eat I have diarrhea? I have not had a solid BM in almost 3 months, back when I got really constipated and had to take a laxative...  
I am 18 weeks and can't seem to gain any weight either... 
Has this happened to anyone before ?