Hi boxhead (?)
Welcome to the forums. We get a lot of threads from carers, so you're not alone.
I suffer from a variety of mental illnesses and I've hit rock bottom a number of times. I can only imagine the worry, fear, resentment, frustration, and loneliness my partner has had to endure. So I completely get where you are coming from, it's a tough job and I don't think enough credit is given to those who love people with a mental illness.
I want to start by saying whether it's depression or something else, you're wife is emotionally unwell. It can be really difficult to see the world through the eyes of someone with ill mental health. They can't think rationally, logically, or practically, this is not by choice. It can be lonely, scary, ruin your self worth, resilience and tolerance, and put you in a place we're you feel raw, exposed, and unlovable. It's possible that the only way that your wife is able to cope with how she thinks and feels is to be defensive.
As you know, it's not easy to speak with someone who is defensive. Having said that communication is something that you will both need to work on together. It's not useful to take the "well it's easier if I shut up" route, and likewise it's not helpful for your wife to become sensitive to everything you say.
I'm assuming that you're wife is seeing a Psychiatrist/Psychologist given the scenario you mentioned with her meds. Have you tried telling her that you love her and that you appreciate every thing she does for you and your family? This positive reassurance is important (don't forget she feels worthless). You could then let her know how important your relationship and your family is and because of this you'd like to get some support to help support her. You could offer to go to an appointment with her, or ask if she'd prefer you to see someone separate.
I know it's really difficult to be the one who feels like they're working hard, and making sacrifices. My partner is in a similar predicament. You also need to take time out for yourself, even if to go to the gym once a week, go for a bike ride, or join a walking group. You need time to refresh yourself. I also wonder whether you can lower your expectations of her for a little while. I know you see it as all she has to do is school drop offs and be a mum. From her perspective she struggles just to have a shower each day, so she may feel that she cant meet your expectations.
I hope some of this is helpful. Let us know your thoughts.
AG