Pregnant and have diarrhea

Im 3 months and just this morning i got diarrhea which is weird because before i was just constipated. It must of been something i probably ate but yesterday night i got a burning sensation on my stomach that comes and goes. I also just threw up. I got no pain besides the little burning that comes and goes so i was wondering if i can take something. Like i got some Alka seltzer? Just for tonight.