I presume that your gynae performed the ultrasound scan to rule out PCOS (given that you also have irregular periods).
You have a cyst in your right ovary - cysts are very common in women who are still ovulating, and are almost always benign (none-worrying, and go away by themselves).
This can account for the difference in size between your ovaries. Ovaries are usually NOT of exactly the same size, and range from about 2 - 3 cm x 2 - 3 cm in size.
If your ovaries are otherwise normal in appearance (as the report suggests), there is no reason for concern. If you are particularly concerned about the difference in sizes or any other period-related symptoms, do follow up with your gynae, who will be able to advice if you need further follow-ups and scans.
