Since your baby is already 10 months old and you are only going back to work 1 day/week, it seems a bit challenging to you and to him to transition him to formula for just 2 months and then later transitioning him to cow milk. Since you've already been pumping and your baby has no problem with bottles, is there any way you can work on pumping enough of a supply during the other 6 days/week so that you can perhaps only pump once per day while you are at work? If you don't pump at work but are still nursing full time on the other 6 days, you'll probably feel engorged and uncomfortable by the end of your work day. If you are already thinking about weaning, it might be easier to just put it off until you can transition to cow milk. My daughter has a cow milk allergy, but when I wanted to transition her to goat milk at 15 months, I started out just putting a splash of it in each sippy cup of mostly breastmilk. Then after a week or two, I would increase the amount of goat milk by 1 ounce (and decrease the amount of breastmilk by the same amount). When her cups were 75% goat milk and 25% breastmilk and she was drinking a good amount per day, it was no problem to just make the full switch to goat milk cups. It took us almost 2 months before I could send her to daycare without breastmilk and all goat milk, but I don't think she really noticed the gradual change, even though I still continued to nurse her in the mornings and evenings. By the end I was only pumping once a day and only getting out 2+ ounces, but that was all I needed. I never had issues with engorgement or clogged ducts, etc. BTW, she was fully off bottles and used only sippies and straw cups by around 10 months, so you can think about whether your son is easy going with change or whether you just want to make the transition from bottle to cup at the same time. This is probably not the advice you want to hear (to basically put off weaning for another 2 months), but it seems easier for your son to handle a big change of milk just once... Maybe you can talk to his pediatrician about introducing an ounce or two of cow milk a day at 11 months so that you can begin the process of full weaning a tiny bit earlier??