Almost 3 week period!?

Emily
Probably the first five days it was a very light bleeding, Like spotting and then it became more like a period for the next week and so on so forth. It stopped last Saturday & had sex. Today(Monday) I woke up spotting again and when I wiped it was very light pink. Also I've been expieriencing pains in my lower tummy. It will vary from side to side. Help! Is something wrong?