Yea cycles change throughout your life. The older I got the worse mine got though lol. Isn't anything to worry about.
There is nothing wrong with your menstrual periods. However if it persists then it needs evaluation for oligomenorrhea. The causes could be benign tumors of pituitary gland. It could be due disease of thyroid gland like thyrotoxicosis, hormonal imbalance, pcos (cyst in ovary) etc.
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.