27% chance of being pregnant!?!r

Ok so I'm kinda flipping out. So me and my boyfriend had some fun and we made sure he wore a condom. It was too small for him but it still some what fit. So after I got off of him the condom was filled at the top and then it was only half way on him. I didn't check to see it leaked. Should I be worried?!?

UPDATE: ok so I talked to him and he said that it didn't leak. Because all of it was still up at the top. Also he did put it on correctly, we made sure. Also I had just gotten off my period, the 9th and then my fertile window opened the 16th.