Please don't worry about the rotavirus! DS1 (born Jan 2013) didn't have it as it wasn't on offer. DS2 had horrendous reflux for the first 10 months of his life, which pushed me to the edge at times as it took ages to find the right combination of formula (I didn't BF either of them) and medication. He had the first dose of rotavirus but it made him so sick and he had such an upset stomach that I really was on the edge. I took him for his second but spoke to the nurse about the awful side effects he had and we decided after some discussion (and a few tears) that at that point the benefit to him was probably not worth pushing me over the edge and not worth making DS2 suffer more than he already was. Yes, there's a tiny risk, but no more than DS1's risk. I felt awful for a while afterwards because I fiercely believe in immunisation. I have the benefit of hindsight and having had time to think about it. It was the right decision for my DS2 at that (truly awful) time in our lives. Things are better now. He's 18m, healthy, cheeky and I love him to bits. But we spent 10m in daily hell.
Give yourself a break! Try FF as others have said. You might feel better physically and less drained. I was FF, my siblings were FF, and I was in no fit state physically or mentally to BF DS1, so they've been FF too. No harm done, all healthy, all bonded just fine. Also FF would allow others to take on some of the workload.
Try to stop worrying about the rotavirus. Only recently introduced, so millions of people put the who haven't had it. Whatever decision you made, I'm sure was the right one for your DD at that particular time. The risk is tiny and no more than your DS if he didn't have it.
Give yourself a break! This parenting stuff is way harder than anyone ever tells you. Go back to your GP and sort out some more meds. Don't give up. You can get through this, it just takes time. It would take less time if your DP was a bit more helpful so instead of giving up on your kids, give him a kick up the behind! And if MIL wants to have the children...great! Let her take them for a few hours a day to help you out or for a few days to give you a proper break (don't forget to pack the formula!).