Inserted the tip only for a few seconds

My gf (24F) and I (23M) tried doing raw for the first time. We went to the bathroom to take a bath and then made out a bit. Before I inserted it, I made sure to wipe the precum off the tip by using the shower head and the water was cold. I thrusted a few times and only felt half of my penis going in (I didn't cum inside her). I then pulled out and then we finished taking a bath.

I checked her calendar and we did it 3 days before her fertile period. We don't use any other form of birth control except for condoms. I know there's still some risk of pregnancy but I'd like to know the chances of it. Is it likely or unlikely in this scenario?