I don't know what this could be?

I have very regular periods. I get them on the 7th of every month with very noticeable signs a week prior to starting. So, in July I got it on the 7th as normal but then I was bleeding again on the 21st of July but it was light and only last 1 day. Then all through august I have felt miserable. I'm so tired I can barely stay awake, my boobs hurt and grew quite a lot, I've been very nauseous and headaches. These aren't my normal period symptoms, I haven't even had any period symptoms this month, at least none that I'm used to getting. But yesterday (august 26) I started spotting and it could only be seen when I wiped but there was a painful amount of pressure in my lower abdomen and I just felt really awful. So today (august 27) I woke up with an awful pain in my side and really bas cramps and I was bleeding a bit more than the day before, I took some Tylenol and crawled back into bed. When I woke up again, I was done bleeding but there was still discomfort in my abdomen. I feel pain free now but I have a killer headache. I've taken one test and it was negative. So, I'm not sure what to take from all of this and any insight would be very helpful.