Infertility. After taking medicines!

Hi I'm married for 3 years now and trying to conceive from 2 years .ihave pcod my periods are irregular and hypothyrodism.i had ovulation induction with times intercourse for 6 cycle but all of them were failed.my doctor suggested diagnostic  hysterolaproscopy in which everything was fine and then tried ovution induction with time intercourse again for 3 cycles .I never had follicular study in those cycles my doctor told that it was not necessary.then i had 3 failed IUI s in which I came to know that my endometrial thickness was not up to the mark and took the medicines for it and it improved to 10mm.my doubt is that in those 9 cycles of ovulation induction my endometrial could be less probably that could be reason it failed?if yes then we just had 3 failed is the trial enough before   moving to IVF considering the fact that there was no follicular study in the previous ovulation induction and i had low et in the 3 IUI cycles and improved only after taking medicines