The anticipation of it is actually far worse than the actual pain.  I know it's scary cause it's a good size needle, but honestly it isn't bad at all--or at least most times it isn't.  There may be a few times near the end where it hurts a bit more.  All you'll really feel is a stick, and then some pressure as the saline fills the expander.  I'd recommend taking some Tylenol before going, cause you will be sore afterwards.  You will have some soreness/tendernness for the first few days, but will wear off just in time for your next fill.  It is possible to have some pain in your ribs or shoulderblades from the pressure of the expander.  This pain will be relieved once the expander is replaced with the implant.  This next month will fly right by, and soon you'll be getting your implants in.

Good luck!

Angi