From what I pieced together through the tears your lack of grammar made me cry:
If the condom tears its because you were: a. using it wrong or b. defective.
I get the hate for Trojan for being over priced but I'm a fan, sort of. I can buy Durex and have vice around my cock and writhe in pain or I can something comfortable.
Piss doesn't kill precum. There most likely was some you just lost it in your girlfriend or there wasn't any which happens.
Precum or not you are letting sperm out once you reach a certain state of arousal. The chances of your girlfriend becoming pregnant depends on her really and several factors.

Based on the fact you have a "pop" in there I'm guessing you shoved your dick in a condom and left a bunch of air in the tip and then end up getting some suction or something going on popped the damn thing.