Had this myself when DS was 4 mo, and I went back to work when he was 6 mo, although I was able to be very flexible and breastfeed him in the morning, then pick him up early.
Tried everything, and I mean everything, and he would not take a bottle (or syringe, or cup). He would not 'take some milk when he is hungry enough' - nope, he'd rather starve to death than take a bottle. Jam on the teat didn't do anything; he cried with his mouth closed whenever anyone tried to force him to drink from a bottle. (Amazing, really, that such a small baby can be SO DETERMINED!)
Now, this is a worst case scenario, and I remember being so distressed and upset and stressed out about the whole thing. You may find some of the suggested tricks work - and I hope they do for you!
If not, this is what we did: when he was weaned, we focused on giving him weetabix with ebm (or formula or whatever), cereal, yoghurt, cheese etc. He would not drink milk but we tried to ensure he ate plenty.
With bfing, I tried to keep somewhere near the same number of feeds - one in the morning, sometimes two if I could take him to nursery a bit later; then I would pick him up as early as possible, feed him immediately, and feed a couple of times in the evening. He also fed at night (darn it!! 
).
Incidentally, yes, they're supposed to get lots of milk at their age - 500ml or more I think? (I fixated on that!) but DS did not get that amount. He is - and always has been - in rude health, no weight losses, no sickening, teeth are fine, bones I guess are great... It's easy for me to say to you now, when you're in the middle of it, that later on you'll look back and wonder what the fuss was - but you will! 
But I hope you find a solution - it's such a big worry.