My period is irregular and sometimes it's comes every 31 days and sometimes it can skip up to 3…

My period is irregular and sometimes it's comes every 31 days and sometimes it can skip up to 3 months. Well two weeks before my period I usually get sore breast and heart burn, a little gassy too. And about 1-3 days before my period I have cramps. It's kind of hard to tell if I'm prevent of not. My boobs don't hurt but my nipples do. Saturday will be 31 days and I've been cramping since yesterday. My stomach feels week and I've been burping. Took a test on Tuesday and was negative. What do you all think?