See a fertility specialist, it's time. Normally we don't consider a fertility problem until a year has passed.
The irregular periods can indicate a hormonal problem. The birth control can mask that.
You can expect a complete physical and internal exam, including blood work. Your partner should also be tested, he can expect a semen analysis (sperm count).
Ideally you'd be having sex just before ovulation but that can be hard to determine if you are irregular. Monitoring your cervical mucous is one way, body basal temp is another and there are also ovulation test kits available.
Hope it helps.