31/2yrs ago husband got testicular cancer, removed the whole left testicul, no further treatment, had a son short after, been trying to get pregnant for the pas 3yrs with out success can this be the reason why we can't have another child?

Need to see expert: With one testis still one can have a child slighly reduced sperm count will be enough for fertilization. ( most likely did not have chemotherapy ) see fertility specialist for tests and treatment.

While men with: Testis cancer may have low sperm counts, you had a child after diagnosis. Perhaps you might seek a fertility evaluation, sperm count and motility, but the fertility specialist usually look at both partners, and even with no identifed cause, infertility happens. Get some help.