I searched around JM and couldn't seem to find a forum that deals specifically with your particular situation. I thought there might be a board for those TTC after cancer...

surprising that there's not.

your first step should be getting an SA done on your husband. Ejaculate and sperm are two different things... So his 'cumming'' in a sizable amount doesn't really tell you anything. Most of what we see is semen, the carrier fluid for sperm... You can have plenty of semen but no sperm being carried within it... So, being that your DH had testicular cancer, it's really important that you find out if he is indeed creating any sperm and if so, what condition they're in.
Normally, you
would have to wait til you'd been TTC for a year, but I also agree that considering the medical history involved, you shouldn't run into any trouble having a Dr. honor that request.
I also recommend you getting yourself checked out, if you haven't already. Make an appt with your OB, let them know you're TTC, etc. You can also chart your BBT temps to see if you are ovulating and if your cycles are proper length, etc. We can help you with all that if you decide to...
I do hope you'll keep us updated on what you decide to do and how things go!