Hi !  Due to relaxation in the vaginal muscles,  Seminal fluid slips away post intercourse which may result in failure in getting pregnant. How these will be not the case in not getting pregnant,   As in 1 ejaculation some millions of sperms will be ejaculated in to vagina and out which only one Healthy Motile sperm is needed to reach th fallopian tube to fuse with ovum to get pregnant,  As your husbands sperm count is very less, if motile sperms are also less in the present count, pregnancy becomes difficult what ever position you may wish to maintain. As the motile sperm has to travel from the vagina to fallopian tube to fuse with ovum, it is very much difficult to get pregnant if the motile sperm are not proper in number. So concenterate on medication to increase the sperm count,  That would be enough to get pregnancy in one intercourse itself. Consult a good homoeopath and start medication,  Sperm count can be very easily increased with in couple of mnths through homoeopathy. Dont lose hope,  as many such infertile cases have been made fruitful through homoeopathy.  I wish u have fruitful family life.