Having two young children can definitely make someone feel like they are going crazy. On top of that we are in a pandemic and your spending so much time together as a family. Have you tried sharing your feelings with your wife? About how she is making you feel more than the fact that she "is changing". Having kids makes us change and breastfeeding has our hormones out of wack. Maybe she is not aware that her hormones are raging. It isn't until we stop breastfeeding that our bodies sometimes reset. Not saying that she should stop breastfeeding.

It sounds like there is a communication breakdown as well. She also needs to tell you what she needs and space to tell you how she is feeling. Since you are both home maybe you can create a schedule for the week that includes time alone, time together as a family and time together as a couple. That will help normalize your home environment.