I wish I had more time, but I will have to give you a quick answer for now and try to come back later. I went back to work when DS1 was 7 months, and again when DS2 was 8 months. I continued bfing both boys, so it can definitely be done. My boys wouldn't take a bottle for love or money, but did luckily take a sippy cup. However, they never drank from it much until they started day care. Once I wasn't there, they drank EBM in a cup much better than they ever had at home. They know when mum isn't there with the breast and don't usually starve themselves. More than likely you will find your DS is the same. And really, at that age, he is on solids and will drink some water, if he doesn't drink the EBM, he will be ok until you pick him up and give him a bf.

If it was me, I would keep his routine as it is now. It's what he's used to and it's working for you both. Day care will follow your routine at that age. He will be fine to have EBM instead of his usual bf, and you will find your supply will adjust so that you can bf when you are home, and be ok when you're at work (you might have to express a little in the beginning until your body adjusts though).

Both times I found the thought of going back to work was harder than actually doing it. My boys adjusted well, and much to my surprise, so did I. So try not to worry too much.

If you have any more questions, please ask. I am happy to share my experience.