How long of a stretch have you left him for? Are you giving the bottle attempt an hour or two? I know how frustrating this can be. Before I finally gave up on bottles, my DS would go up to 7 hours while my mom tried to get him to take a bottle. He was a lot older than your baby, though.
I'd try being very consistent about replacing the same feeding each day with a bottle. If he's hungriest first thing in the morning, try that feeding. Could your DH feed him while you pump? I have a friend who has been very successful getting her babies to take bottles by always having her DH do each and every early evening feeding while she pumps.
Something else to try is to see if you can sneak a bottle in while he's sleepy. I've heard this works.
My last suggestion is a baby nurse or doula. Someone in DS2's music class tried this with her baby with some success. I think she hired her to come for a few days in a row.
Good luck!
Tara
living a crazy life with 3 boys
I am thinking now
of grief, and of getting past it;
I feel my boots
trying to leave the ground,
I feel my heart
pumping hard. I want
to think again of dangerous and noble things.
I want to be light and frolicsome.
I want to be improbable beautiful and afraid of nothing,
as though I had wings.
~Mary Oliver