I Was On Clomid For 2cycles Of 50 And 100

I was on clomid for 2cycles of 50 and 100 mg... with 50 mg I had 1mature follicle 18mm in size on cd13.. with 100mg I had 3 very small follicles on cd 13..
My doctor then changed my medicine to letrozole2.5 mg.. and on cd13 I had only 1follicle 14.8mm.. my doctor said she would try 1more doze of letrozole and if I still dnt get enough mature follicle I would have to consider fertility treatment..