Hello,
The cause of irregular periods could be due to hormonal imbalance, stress, chronic illness, polycystic ovarian disease, thyroid gland disorders or diseases, pituitary gland tumors or cyst, galactorrhea, prolactinomas etc. You should consult a gynecologist and get examined and investigated as soon as possible to know the exact cause of all these episodes.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
I feel I should add I have posted this question for a close friend who is here with me and my profile and posts show i am pg but as far as we know she has no idea whats going on with her.