What would next step ttc be if we have been trying for 4 years. i have already done hormone check, scan of brain for gland, ultrasound, post coital test all fine except husband sperm little bit low?

TTC: If you have had prolonged infertility, you should seek the help of a reproductive endocrinologist.

Go see a specialist: most healthy couples should be able to conceive within 2 years, since it has been this long consider seeing a reproductive endocrinologist, your family doctor or ob/gyn should be able to recommend one to you. A next step if your husband has a low sperm count would be an IUI or intrauterine insemination, where a doc takes your husbands sperm, washes and concentrates it and injects it into you

See a specialist: If you have been trying to conceive for more than a year without success, it is time to see a specialist in fertility medicine, also know as reproductive endocrinology. You don't mention testing for tubal patency and blocked tubes can cause infertility. The specialist can review all your test results thus far and let you know what your treatment options are. Hope this helps. Best wishes.