Zero Sperm, taking Clomid

Hi Everyone tried reading through posts but figured it would be quicker just posting the question. Husband and I have been trying for almost 3 years and we recently found out he has zero sperm count. 3 months ago we tried the sperm retrieval process to find out there was nothing there for them to take. The whole thing is a nightmare and I know we have options available (adoption, donor). They dont know the cause of it and if it was always an issue based on a past relationship my husband had. My husband had started Clomid and will be going back in 6 months to see if it helped at all. Has anyone had any success with this? Or recommend anything else to take along with it?