Getting pregnant while breastfeeding!

Hey everyone!.

I'm new here and looking for some insight.

My DD is 11 months and we're nursing on demand still. My cycle returned last month Oct 15-oct 23. My hubby and I are anxious to try for another baby since he was recently diagnosed with testicular cancer and had a testicle removed. He has a high chance of reoccurance and we want another baby close in age to DD and know that Chemo and radiation will kill his little guys completely. I'm wondering if anyone has had issues conceiveing while nursing?