We are in the exact same situation with a 2 year old. Except my DH's Test levels were a lot lower than that and we are a couple years older. It was after we had our DD that he found out about his low levels. He then went on test replacement for over a year. After TTC 9 months we saw a specialist who told us to get off the test right away. That month (Jan) we got pregnant, but it looks like I am going to miscarry. I had a chemical pregnancy a number of months ago too.
Sperm quality could be an issue, but the only way to tell is get a SA and have a reliable lab/Dr check it out. He had one six months ago that came back ok (low end of normal), but then the specialist we saw wanted another one to look more closely at the quality of the sperm. (we didn't do it, since we got a BFP).
Now he's having his FSH, FH, and prolactin checked. You should have these checked too to see what is causing the low test. He's just been referred to the endrocronoligist specialist, so we don't know yet. It could be a tumor, test failure, or a good portion are just unknown/genetic.
It's important that you don't go on TRT as too much test can harm your fertility. There are other options, FH or hCG shots that could help your body produce the test naturally. We will be looking in to this in the coming weeks/months to see what is best.
I'm hoping the MC's are a genetic fluke for both of us and next time will be a success!
The chemical pregnancies are a good sign that something is working, so just try to stay positive (and get yourself checked out for your own health).