If the condom doesnt break or leak, you cant be pregnant right? checked condom by filling w/water after sex. it didnt leak water at all.

Unlikely: With proper condom use, it is highly unlikely to become pregnant. The only true prevention is abstinence. You still have a very small percentage risk but if the condom was water-tight as you describe it is low risk.

Failure rates: Any form of BC other than abstinence has a failure rate. Properly used and fitted condoms have a cited failure rate of 1-3%/yr of use in some studies. Misuse including reuse of condoms, improper fit, not applying before initial penetration, etc. all increase failure rate.