Millions - yes millions - of sperm are in each ejaculation - so even though some comes out lots stay in. BUT if you are trying to get pregnant there are a few things you should be doing a little differently.
#1 Only do it once every four days. That way you have the largest quantity of sperm in the first ejaculation when you have sex. ( And he should also not masturbate during that time.)
#2 After you have sex - don't get out of bed for 20 minutes. And elevate your legs and pelvis as high as is comfortable.
#3 Have sex in the mission position with your butt raised on a pillow. ( I suggest you get a waterproof pillow case.)
#4 Get a special calendar. Mark day one of your menstrual period on the calendar as 1. Put the number on each day until you start to menstruate again. This way you know how many days it is between your periods.
#5 Start taking your temperature every morning before you get out of bed - and then chart it on a calendar. You can take your temperature any way you like - just be sure it is a good quality thermometer. Your temperature will go up very slightly when you start to ovulate - so once your temp goes up your period is about to start and you won't be able to get pregnant for about 10 days.
#6 Check your cervical mucus. You do this by dragging your finger across the entrance to your vagina and collect some of the mucus if you have any. Rub your fingers together and see how it feels. You don't have to do it during your menstrual period. Once your period stops you should have very little cervical mucus for about 3-4 days. Then it will become thick and sticky for about 2-3 days. They for about 3-5 days it will become very thin, slippery, and stretchy - these are the days you most likely will become pregnant ( and your temperature should at its usual temp.) Then your mucus will get thick and sticky again for a few days, and then very dry. Mark this in your calendar too. (M for menstruation, D for dry, S for sticky, T for thin.)
7. Mark on this calendar the days you have sex. After 3 months you should be able to see a very distinct pattern and know when you can get pregnant and when you cannot. You can also take this calendar to a doctor who will be able to see a pattern or the absense of pattern that helps the doctor better help you get pregnant.
Most couples who use no method of birth control will get pregnant in six months. Most people who have not gotten pregnant in six months - and start to use these methods will get pregnant in three months.
SO give it a try - and name your first daughter after me.
Susan