Your sure your not pregnant now? It is three months since you saw your period, sometimes when a woman havent been pregnant for so long dont mean it forgot how, give it a chance...do you give up if your in a car full of gas in the dessert when the car stall...no...give it a chance...maybe its not you ...it could be he hardly have any gas..its not always the woman...
At this point, you are going to need to see your ob/gyn. If you havent already, you need hormonal blood test down to see why you aren't getting your periods. Maybe your doc can work with you to see when you are or aren't ovulating. But it's time to get the ball rolling--the sooner u find out what the matter is, the faster you can work towards becoming pregnant.
Best of luck