OP, I really feel for you.
I had to exclusively express with DS for a few months. It was bloody hard and really was the worst of both worlds - all the faff of ff with the round-the-clock relentlessness of bf. I also suffered with blocked ducts and got mastitis four times, which made a tough situation even worse.
I got through it with dogged determination but, after that experience, I know I won't do it again with a second DC. It ruined those early months with my son as I was ill and exhausted.
Besides, second time round, I'm not sure I could cope with a three-hourly pumping schedule tying me to a hospital grade pump, as well as a newborn and a toddler.
Call me selfish, but bf is but one part of raising a child. Yes, breast is best, but the alternatives aren't dire. Curiously, my DS only learned to bf from the "source" when he was three months old, after having formula top ups on top of my expressed milk. It got a whole lot easier then, and we were able to bf to a year.
Suddenly we'd gone from a sickly and underweight baby who'd been readmitted to hospital twice, to a thriving and healthy little boy. I may be wrong, but I firmly believe it was the formula top ups that gave him the strength to learn to breastfeed. And once we could do it, it was so easy - no longer tied to the industrial pump, we could leave the house for full days, visit people, go for walks, do baby groups, explore.
My advice would be to take each day as it comes. Topping up with formula is fine, moving over to formula completely is fine, using formula for a bit while you also try to reestablish bfing is fine. It honestly isn't the be-all and end-all (eyes toddler, who I struggled so much to bf, climbing up the cupboards to scoff handfuls of jelly babies)