I have had my period 3 times in the 3 weeks. it lasts about it 2 or 3 days but now my stomach very hard and very swollen. with bad cramping.

Get evaluated asap: your description could mean a lot of things , but i am assuming this is sudden onset and is not routine ,it can be a pelvic mass or tumor etc you could be pregnant. or it can be totally not a GYN cause and you might have some GI related event like IBS etc. i would like to get more information from you to help you guide which direction to take