After ejaculation from intercourse, the sperm are well on their way deep inside the vagina headed for the cervix to get to (hopefully) an egg awaiting fertilization. Urine won't come in contact with the sperm at this point...so the answer to your question is no, urinationg after intercourse will not keep you from getting pregnant by killing the sperm.
There are a number of factors that affect fertility. If you're trying to conceive and having difficulty, the best thing to do is talk to your doctor. Even if you have conceived and given birth before, the older you get, the harder it is to get pregnant again. In many cases women experience hormone deficiencies that keep them from conceiving a second time. This situation is easily remedied by a prescription hormone (usually Clomid) that will make it easier for you to get pregnant. And another thing....the position during sex has NOTHING to do with whether or not you get pregnant. If a woman's vaginal mucous is normal and her body chemistry is not harsh enough to destroy the sperm inside the vagina...then she can get pregnant on top....on bottom...standing up...on her head....you name it. If the little sperm-guys can swim...they don't care WHAT position you have sex in....you can absolutely get pregnant.
There are a number of factors that affect fertility. If you're trying to conceive and having difficulty, the best thing to do is talk to your doctor. Even if you have conceived and given birth before, the older you get, the harder it is to get pregnant again. In many cases women experience hormone deficiencies that keep them from conceiving a second time. This situation is easily remedied by a prescription hormone (usually Clomid) that will make it easier for you to get pregnant. And another thing....the position during sex has NOTHING to do with whether or not you get pregnant. If a woman's vaginal mucous is normal and her body chemistry is not harsh enough to destroy the sperm inside the vagina...then she can get pregnant on top....on bottom...standing up...on her head....you name it. If the little sperm-guys can swim...they don't care WHAT position you have sex in....you can absolutely get pregnant.