I have a gfci, light switch, and bathroom fan/light. I have all blacks to blacks wired together and whites to whites. It worked before on a basic light, and I have checked all connections it will only run through gfci, if I turn on light it will short out the circuit. Any ideas

Recheck your wiring, you might have had an unmarked switch loop. Start with the power lead to the line side and the incoming neutral. Than, check continuity with a VOM to make sure you are not trying to backfeed into the GFCI. Did you put the fan and light on the Load side?