I had a very hard time at first trying to pump! I have the Avent Isis pump. It has taken some time, but now it is much easier. If you can explain exactly what you were doing, I'm sure I or someone else on here could offer some tips. Seriously, at first I thought it was never going to work, but now I've got it figured out.
On another note, a friend of mine pumps with the Isis, but her baby wouldn't take the nipple that comes with those bottles. So, she bought the Playtex starter kit that comes with several different nipples. She tried each one with her baby, and did find one that her baby would accept. Have you tried ever nipples?
One other thing, now that nursing is well established with my baby (10 weeks now), he will not accept any formula. I have tried. Once he accepted it spoon fed into his mouth, but that was an isolated incident. The only way he will eat when I am not around is my pumped milk. Perhaps your baby is the same way.