Hi, How Big Is The Chance That I Got Pregnant

Hi, how big is the chance that I got pregnant yesterday if 2 weeks ago I had my period (it was a week too early cause I forgot to take my pill once) but I kept taking my pill tho that week, a week after that, my period ended and it was also the week I didn't have to take my pill. So I had a pill & period free week. I started to take it again on friday (I always start taking it on friday). So I have been taking my pill for 3 days and on the 4th day I had unprotected sex. Do I have to get the morning after pill, or is this unneceessary? I still got about 5 hours to get it. Thanks a lot !