Condom effectiveness?

If your partner leaks before he finishes, are condoms still effective? Wondering if it will get pushed out? Im having a terrible time finding anything on internet about it. Yes I know to ask a doctor and I will, but it's probably too late and yes I'll test.....I am just curious what responses I'll get here. I feel pregnant but racked my brain on how that could be possible because the condoms never tore......then I remembered his issue and figure that must be it....or.....my body just likes poking fun at me giving me prank pregnancy symptoms.