one thing to try is to have sex with you laying on your back (missionary style) but put your bottom up on a pillow to elevate your bottom a bit. this allows him to penetrate you a little deeper (good for when he ejaculates) and it will also keep you from having the sperm leak out of you.
one additional suggestion is to have an orgasm! most ppl don't realize it, but when you have an orgasm, the convulsions or contractions that occur work to your benefit in getting pregnant. what happens is that your cervix sort of moves down and opens up just a tiny bit to pick up on some of the semen during the contractions.
sooooo...what you have to do is to have an orgasm almost immediately AFTER he does! you can probably figure out how to make this happen, but if not, just ask and i'll tell you!
i know that the original post on this subject is a year or so old, but this is valuable info to ppl who are trying to get pregnant, so i thought i'd post it anyway.
jasmine