Ah man...seems the blood test is more accurate than the urine test. For a chick that apparently would have difficulty getting pregnant (who knows 'how'/'why' she knows this)...it all seems a bit odd. Sleep with her once...and gets pregnant "easily". Very odd...like the others say....do not marry her and think it will help make it better for the kid/situation etc, blah blah. I almost get the feeling she wanted this to happen...as you guys seem to know each other for a while, and hooked up previously. Added...the quickly made decision to keep the baby...like I say...it all seems a bit odd...
Strongs dude, it's a big thing to happen to someone...just try take a 3rd party perspective and don't commit to anything unless you are 100% sure you are in it. It's an 18 year commitment at the least supporting the kid financially, emotionally etc. If you are not up for it, rather walk away.