Right, stern talking to...
1. Feck the fecking housework
2. You've been ill. Give yourself a break
3. Work isn't going to be instantly easy. Was it when you started your job? I doubt it. You need time to settle in again.
4. Imogen is putting on weight, Doesn't matter if it's slow, as long as it's going in the right direction, she's happy and you have wet and dirty nappies. My LO put on weight v slowly (dropped from 50th centile to 9th) until weaning, when she started to pick up. At just a year she's now approaching the 91st centile and I'm wondering why I worried so much.
5. Ranting is fine and good to do on occasion, and here is a great place to do it.
6. This too will pass, Never forget that.
You have a lot to cope with at the moment, sounds like you are doing a grand job 