I was just contacted by a 19 yr old girl claiming she's my daughter...I'm skeptical...what should I do?

If it is possible that she is your daughter then I would see if she is willing to take the test to see if she is if you were to pay for it. If she is then you should call up your lawyer to see if you are liable for those years you missed (I doubt that you will be because the mother wouldn't allow you to) and even if you aren't liable I would still try and pay for some of her expenses it just seems that would be the right thing to do. If she isn't then no big deal.