im not a IVF or assisited preg mummy but i had to use progesteron pessaries to keep my cervix and uterus calm.....

i was on one in the morning and one at night.
i had to elevate my lower half, just put a pillow under my butt, for 30 mins after insertion (sorry couldnt think of a better word).

i agree with the use a liner or wear ur old crappy jocks coz they can make a mess found that out the hard way unfortunatly!

you do need to be weaned off them, i was on them until 16 weeks, so when my OB decided to start weaning me off them i had to cut down to one a day for a week, then one every second day for a week and then stop them.

good luck, hope u get a BFP!