A.R.
While you are probably not pregnant, I would go to the doctor anyway just to be safe. If you have gotten pregnant it is possible that it is an ectopic pregnancy and that is best caught early. Either way, you will feel much better after having gone to the doctor.
Now, women can usually get a bit of substance out of their nipples if they try after having a child. That's nothing to worry about. The pains sound like you could either be ovulating or preparing to start. It is also possible that these signs are indicative of another problem. I would really go ahead and go to the doctor. Better safe than sorry, I say.