What Causes Irregular Menstruation When Diagnosed With PCOS?

Hi, I a m 27 years old gorl, married from last 2 years. In feb 2015, I was diagnosed with high thyroid, so i was put on 100 mg thyronorm. Now my thyroid is absolutely controlled. My periods are irregular since from the start, sometimes the gap is of 2 months , 1 month or 3 months as well. But recently i have diagnosed with PCOD, although the condition is not that bad, so my gynea has put me on Fermilion for 21 days.. My question is that I am planning to conceive this december, but i am afraid because of my irregular periods, PCOD and thyroid as well... Apart from medicines and all, i m trying to control my weight as well... Will I be able to have a normal pregnancy Gunjan