Never Been Normal

Hi,
I am 21 years old and female. I've never been regular, usually only once a week, and that worked fine for me. I'm only 5ft and weigh 92lbs. I figured, for me, this was my normal.
I am studying abroad for the first time and am currently in England. Over a week ago, I started developing strong gas pains, which lead to diarrhea. I figured it would go away after a few days, but it has become a cycle of gas pain for a day or 2 then a day where going becomes crampy and painful and, although the diarrhea is passing, I always feel it will return.  I am not sure whether it is just developing to a new country or homesickness or something wrong with me personally.
Please, help.