Hi, We A Boy Who Is 5 And Half Year

Hi,
We a boy who is 5 and half year old and we are trying for the second baby, but with hard time. when my conceived normally for the second baby she want to take some time for the second kid and it end up being a abortion. Later when we tried pregnancy was positive but no heart beat and growth to the fetus. (we noticed that TSH level was too high for my wife.) Doctors did D & C. then the problems started. we have been trying for last 3 years now but no positive pregnancy. my wife is using thyronorm 50 mcg and her thyroid profile is under control. we did most of the tests related to infertility like fertility profile, semen analysis, antibodies, folicular study, endometrium thickness etc and everything came as normal. my wife has regular periods with 28 days cycle and we have been tacking the ovulation cycle and having intercourse. unfortunately nothing happens. this month she has 10 days delay in her period but again negative pregnancy.
any inputs/thoughts would be greatly appreciated!!
thanks.