Discussing different fertility med

Chelsey • 2 years of Trying for our 1st Baby, now working with fertility DR. In the midst of the storm,God will be your Sunshine!
I have been on clomid for 4 months now and at 100mg and doc told me he only wants to do 1 more month and try 150mg and if that doesn't work he wants to discuss puttin me on letrozole. I haven't ovulated once. I do get good size follicles though. Has anyone else taken this and got pregnant? Did you have bad side affects? 
I read that it was a chemo therapy and the side affects was stimulation of ovaries so I was a little skeptical.