Infertility ruined my marriage

My husband and I have been married for a little over 2 years, and have been trying to get pregnant the same amount of time. After many appointments and a ton of procedures, I was told that it was "uncertain" whether I'd ever be able to conceive children without assistance. But nobody knew why. We tried six months of various assisted fertility treatments to no avail. One morning I finally woke up and decided I didn't want to try anymore. I was mentally and physically exhausted. I told my husband if it was supposed to happen, it would, but I was done trying to force it to. He decided that was his opportunity to leave. We've had many long talks about it, and I've done my fair share of trying to make him stay. But, at the end of the day, he decided his dream of having kids meant more than staying with me. He's been my best friend for 6 years, and my heart is shattered. How do you just start over?