how and when ovulation stops?

Hi,
Welcome to ehealthforum.
Irregular periods, along with long gaps between periods in absence of sexual activity could suggest changes of ovarian cysts, PCOS, hormonal imbalances etc. Do not ignore your symptoms. You should consider visiting your doctor/gynecologist for thorough evaluation and further management. If pregnancy is suspected, consider visiting your doctor/gynecologist for thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). If pregnancy gets ruled out, go ahead with getting thorough investigations done (hormonal and blood work-up along with ultrasound scan) to look for the exact underlying cause for your absent periods. Treatment as appropriate (based on examination findings and investigations results) would be started to help you. Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Drink plenty of water. Take adequate rest. Maintain healthy diet and lifestyle.
Take care.