So freaking discouraged ...

Starting my 3rd round of Letrozole soon. I’ve ovulated both cycles but haven’t gotten pregnant. I have two little girls and my husband and I are trying for our third and final. I was just diagnosed with PCOS in July, according to my doctor, I just recently developed it. Should I get an HSG done to check my tubes or keep going with the Letrozole? I hate this. 😩