I began birth control about 6 weeks ago and I'm not sure if these...

I began birth control about 6 weeks ago and I'm not sure if these things that have been happening to my body are because of it. Anyone had severe stomach pains, so bad that you have to go to the hospital and you vomit? Also, I have been constipated for several weeks. The past 3 out of 4 weekends, I have had horrible stomach sickness with fever, vomiting, and diarrhea -anyone else experienced this? Also, will this extreme breast tenderness ease up?