Can anyone help?

Ok so AF is irregular, so I don't actually know if I'm late but I've been having weird symptoms this whole week. I was a little crampy off and on yesterday into today. I took a hpt this morning and got a BFN, but tonight I've started feeling very bloated and have a "heavy" feeling in my lower abdomen that is now constant with random sharp pains. I have never experienced this before and I am not sure I should be worried. Has this happened to anyone else and what is it??