In your situation with a limited response to Clomid, it is reasonable to try ovulation induction using Fostimon.  Fostimon works in a different way to Clomid as Fostimon works directly on the ovaries to stimulates egg production whereas Clomid increases the level of hormones in your body that control egg development.  As you have PCOS with irregular periods you are less likely to ovulate without treatment but it may happen occasionally so you should continue to try naturally.