Right after my BFP I had a small bit of pink spotting on the TP. It was right after a BM. I had been constipated and having diarrhea off and on.
Have you had sex recently? Your cervix can be irritated that can cause some spotting. Have you been keeping water down? If you get dehydrated it can cause cramping and a little bit of spotting. Take some colace (its safe) and eat some Fiber One. Once you pass the stool you'll find you feel better.
If it gets heavier to where you are filling up a pad or you start cramping to the point where it is seriously painful then I would give your OB a call. Good luck. I know its frightening.