Irregular painful Periods. Is happening?

Hii I usually have period cycle of around 35-40 days. But at times it gets earlier. In last few months whenever i consume contraceptive pills i get flow in mid of the month also and i have spotting 2-3 days in advance of my actual periods.. last month's period was really painful.. after a few hours of when it started i felt some pain that was more than usual periods cramp.. i even felt dizzy and was not able to stand.. my whole body started vibrating. Somehow i managed to reach to the couch.. then started an unbearable pain.. i was sweating as hell.. my mom managed to calm me a bit by rubbing my feet n legs.. i am not able to judge why this is happening? There is a bump in my left underarm which dries up and comes back.. but this time it's been more than a month.. its there..