Hi Karma,
Sorry can't help you with the progesterone shots.

I am on the vaginal pessaries also. I second Xrayen's....YUCK!!
But I did have the swollen belly after the transfer. As a matter of fact I still have it.

I'm 6 weeks pregnant with twins and I look like I'm about 4 or 5 months pregnant.

I had the RE look to see if I had fluid in my belly (due to hyperstimulation) but I did not. Also, my ovaries are back down to normal size. So I'm not really sure why I have a pudgy belly right now. I wonder if it's a side effect of the meds.
Good Luck to you! Maybe your belly is enlarged because you are pregnant.
I look forward to hearing your results.
Sending lots of BABY DUST!