Sex 4 days before ovulation??

Looks like I probably ovulated on 4/21. Had sex 4/17. Do you think there is a chance? I know sperm can live up to 5 days, but how often does it really happen that you get pregnant that many days before O? Has this happened to anyone or know of anyone. This is going on 8 months of trying for us after 3 miscarriages.