[Pinkie_]

I had the same problem at first with my medium domes.. thought i'd never be able to get them on. Here's some things that i tried to make it work:
Sit while leaning slightly backward or forward
Massage and apply an awlful lot of oil on my chest
Put foam tape on the edges of my domes
Get suction on my left breast first then the right one
Put on a t-shirt (with 2 holes for the tubes) over my domes to keep everything tight

I hope this was a bit helpful.
I really understand the struggle but don't give up!
You can do this!