I used Pregnyl injections about every three days after ET from an FET. I also found that it gave me cramps which were far from pleasant! In total I think I had to have about four injections. It think it is supposed to support the embryo after transfer, an alternative to progesterone. Worked for me because I recently got my BFP after my first fresh cycle failed.
Good luck to you. If your symptoms get too bad perhaps you should call your clinic just to make sure.
