You ovulate 14 days after your period (count days from the first day of your period) Sperm can live up to 5-7 days on cervical mucus! That's only If you have cervical fertile mucus! If you don't the sperm last only 3 days the most, in your vagina alone it only last about an hour die to the vaginal chemical we produce there... Then outside your vagina the semen lives as long as 20 minutes depending on how contaminated the air is or environment and as long it don't dry. Good luck on whatever works out for you hun!
very unlikely you would be pregnant if you had sex on the last day of your period. You would not be ovulating when you're on your period