What is causing my lower abdominal pain?

It all started on Mother's day. I took my mother out to the mall so she can do a little shopping and as I'm walking, I started to get this sharp pain in my lower abdomen. I thought nothing of it and hoped it would've gone away but it didn't. It got more and more painful as the minutes went by. I tried sitting down but it was difficult to do; I felt this immense pressure weighing down my stomach and my rectum. Next thing I know, I was starting to have a hot flash. I came home and laid down right away. I ended up putting some warm stuff on my stomach and it started to get better. The next day, it was still there but the pain wasn't as bad as it had been the day before. It's now Tuesday and I just started my period. I have this theory in mind that it doesn't have to do with my period since I've never had this happen to me prior to a period before so I'm not quite sure what's going on. If you have any insight, that'd be great.