Shrinking dominant follicle after ovula?

Hello there practo team, I have been diagnosed with POI with 0.183 AMH. I have no cycles for last 7 months and miraculously I had one after that naturally. Took clomid and followed with scans, blood work and found dominant by scans with very good  hormone levels. Got lh surge on 17th but also high FSH of 63. I took trigger shot on 18th day to force ovulation followed with ultrasond scan on 19th day. My dominant follice decreased from 19 mm to 16mm along other follice from 11 to 8mm from previous scan on 16th day. Question : Is this sign of ovulation or anovulation? I cannot relay on BBT chart or progesterone test because I was asked to take endometrin insert 100mg from day 21. I am day 22 now. Can you still follice after Ovulation and will it decrease in size like mine did? Any help is greatly appreciated. Thanks in advance.