Our story is a little bit different from the others I've read. I don't remember exactly what his numbers were because in the 2 years we were seeing fertility doctors (3 years trying total) he had several SA's done, and all of them had low numbers in at least 2 areas, usually 3. After trying several supplements, and every suggestion we could find (preseed, legs up, etc.), 2 iuis, and him being prescribed clomid, his numbers were slightly better, but still no baby and our doc still considered it highly unlikely, even with another iui. IVF was pretty much our only option at that point because his numbers were consistently low, as confirmed by 2 different clinics.
After a few months of just having given up because we thought it would never happen and we couldn't afford IVF, we made an appointment to talk to the clinic about our options for financing it, and we were going to make our final decision once we had all the information from that appointment. I called on the Friday before Mother's Day to schedule the appointment for the following week. But 2 days later (on Mother's Day) we got our bfp, and on Monday, I went in for the blood test to confirm it. Our doctor's words were "I guess never tell someone it'll never happen."
So none of the other stuff worked for us... I wish I could tell you something that did so you could try that. But what I can tell you is that even if none of those suggestions work for you, it is still possible, even if his numbers stay low.