If I sign my daughters birth certificate and then find out two years later that my daughter is in fact, not mine, do I have any rights? Especially where my ex girlfriend knew the whole time that the baby wasn't mine. Does anyone know if I legally have any rights to her?

As long as she keeps your name on the birth certificate and it is not challenged in court I would say you still have every right to her but getting a court order for visitations would enforce those rights just as her getting a court order for child support would enforce her rights of your paying for the child.

The right to challenge a name on the birth certificte in the US varies by state, in many states there is a time frame, after a number of years, even if you prove you are not the father, you can not remove the name,
But it will depend completely on the state

I am going through a similar situation. After 4 years of my Ex throwing her lawyers at me while I'm overseas. I finally was mad enough to ask for a paternity test because she took my kid out of one day care and put her in another that costs 820 dollars/month. I am responsible for half daycare fees plus 570/month 20 percent of my pay which brings total to 980 dollars/month, in Illinois, now she won't make an appointment to get the DNA test after she agreed to it. Any suggestions?