Is there any difference between mittelschmerz and an ovarian cyst?

Yes. Mittleschmertz is pain at the time of ovulation that can happen with bursting of the follicle and release of the egg. The follicle is a small normal ovarian cyst. The term ovarian cyst usually refers to a larger or abnormal cyst in the ovary. You can have ovarian cysts without pain/ mittleschmertz and vice versa.