FSH of 16 at 43 and trying to get pregnant

I am 43 yrs old and I am trying to conceive.  I have already got a child, however it is proving a bit difficult to get pregnant again!  Went to a fertility clinic today and going through my test results, the doctor said that my FSH of 16 is high.  For the last few months I have been checking whether I am still ovulating  by using over the counter ovulation test, they indicate that I am still ovulating.  Why am I not getting pregnant then?
Thanks

[Elaine Brown, MD]

Hi!
The simple fact is that you are not getting pregnant because of your age.  I hate to be so blunt, but there it is.
Your FSH is elevated, which indicates that menopause is approaching and there are not many eggs remaining in your ovaries.  Those that remain have a high likelihood of being abnormal, so it is possible that you ARE conceiving but that the embryos are not developing or implanting.  
Your best chance for success is with IVF and an egg donor.
It is an unfortunate fact of nature that we were meant (biologically speaking) to conceive in our 20s.  Some women do eventually succeed, so never give up!
Good luck!
Dr B