Time for new birth control?

Hey all! So a few years ago, my periods would get so awful that I would vomit, have diarrhea, etc. Therefore, my doctor put me on birth control just to regulate my periods so this major sickness wouldn't happen. It worked tremendously, but this past period I've been having the worst diarrhea ever (sorry to gross you out). Is it time to switch birth controls? If so, I would like to know how the shot that completely stops your periods (in some cases) works, if any of you have had that shot. Thank you!