Your doctor is correct.
The use of testosterone doesn't kill fertility outright, it does in some men but doesn't in others. In most cases it reduces the odds but there are plenty of men who have kids while using testosterone. Even most bodybuilders have children and they're using massive amounts of testosterone and other steroid hormones.

HCG will help protect fertility. Clomid will make you more fertile.

Clomid is fairly cheap. HCG can be a little expensive if you guy it from a retail pharmacy. Much more affordable from a compounding pharmacy.