I BF both of mine (girl now 5 and boy now 3). I had to cut down with both of them at 5 months as, like you, was going back to work. Since they were quite young we did go to bottles and had to try a lot of different teats - esp with my son, to get them to suck. What worked for my daughter did not work for my son !!. You can buy flatish teats, we got ours from boots, have to tried them ??.
I also found giving them a bottle impossible at first, because they wanted the breast, so the best thing you can do, initially, is to be well out of the way. For our son he would not take a bottle at all, and in the end we had to send him to nursery having had very little success at getting him to take from a bottle. I know it sounds harsh, and it was a worrying time for us, but he soon learnt !!. If he didn't take his bottle, he didn't get any milk. You might find that by leaving your child with someone else, they will accept a bottle.
It's easy to say, but try not to worry, they WILL NOT starve. You just have to be a tough cookie and stick to your guns.
Good luck !.