periods after 2 months and sometimes after 4 months?

Hi,
Welcome to ehealthforum,
The symptoms that you describe could suggest chances of PCOS. It is not impossible to conceive while having PCOS. It can be challenging and take time. PCOS usually responds to treatment with insulin modifiers as most common cause for PCOS is insulin resistance. Consider discussing with your treating doctor/gynecologist about getting started on these along with hormonal contraceptives for better control of PCOS and for regularization of periods. You can also consider discussing continuation of the current treatment with your treating gynecologist (especially if 3 cycles of it have not helped you). Once the PCOS is under control, ovulation inducers would be started to help you have more than 1 egg getting matured to increase chances of pregnancy.
Other causes for irregular period include hormonal derangements, ovarian suppression, thyroid abnormality, etc. It is difficult to comment on the cause for the irregular periods without examining you and going ahead with further evaluation. The exact cause can only be made out after careful evaluation. You should consider visiting your doctor/gynecologist at the earliest for thorough examination and further evaluation to look for the underlying cause for the irregular periods that you describe (you may also consider taking second opinion from another gynecologist). Treatment as appropriate (based on examination findings and investigations results) would be started to help you regulate periods.
When you are trying for pregnancy, monitor cervical mucus changes and the BBT (basal body temperature) charting to predict your ovulation (along with the follicular study if needed) and time your intercourse for having fruitful results. Have intercourse in positions that allow for deeper penetration for high deposit of semen. Have diet with foods rich in zinc content to ensure better maturation of egg and sperms. Take adequate rest. Drink plenty of water. Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately.
Take care.