irregular period????

I had my regular period the 4th-11th. Fertile week the 14th-20th. Then starting spotting the 21st-30th. (today). never have I ever had this happen to me. I'm not on any kinds of birth control. Or medication. I thought it was IB but got two BFN. Thought it was another period, but it's been going on 3.5 days longer than it normally would. never have I experienced two periods in one month. what could be causing this? I have sore nipples, bloating, mild cramps, constant headaches, and a very large appetite. But No positive tests. should I be worried?