I'm Worried About My Wife

I want to say from the start: I am not unhappy or wishing to call out my wife or shame her. But she is having serious issues and I'm not sure what I can do to address them.

I (M33) have been married to my wife (F33) for 10 years. We have 3 kids (6,4, and 1) and a small house and a pretty 'trad' lifestyle insofar as I'm the breadwinner and do taxes and she does most of the laundry, cooking, and childcare. We're very much committed to loving each other.

After the 3rd kid was born she had a severe bout of post-partum depression that she went through an outpatient program for. She got on an SSRI and into therapy, and this managed her symptoms well. She seems happier, compared to before. All great.

The problem: She is really, really tired. All the time.

I get up whenever the kids do and take care of them for usually about 2 hours, get them to school. She's usually not awake at this point, I have to wake her up to take the baby, then go to work. She usually takes a nap during the day. When I get home, she's often exhausted and immediately requests 30-50 minutes upstairs before working on dinner. Every Sunday after church she requires an afternoon nap... that will go 3-4 hours if I don't wake her up. Whenever she isn't actively doing chores or sleeping, she's lying on the couch. She used to take the kids to the park almost daily, she never does this anymore.

The house is filthy. I agreed to clean floors when she was pregnant with our third (she couldn't physically do this herself) but since then she's never come back to cleaning the floors. She's said she will, or that she'll clean under the table after the kids eat lunch, but this never happens. Almost every day after work I have to immediately clean up peanut butter sandwiches, spilled milk, and mostly-empty yogurt cups from the floor. We've had mouse problems, fly problems, ant problems, at least partially worsened by this. The toys get mixed in with all this chum. She's embarrassed about all this, and says she just struggles to get off the couch. I essentially clean everything. If I ask her to help, she'll work at it for twenty minutes and then collapse on the couch.

She's had medical issues. It took weeks to get her to address an issue that was extremely embarrassing and mortifying. The doctor found multiple issues. An untreated infection, weight gain, lost muscle.... she was recommended to do work on her pelvic floor, and I think now after about a month she's both gotten the infection treated and started regularly doing the exercises.

Obviously maybe originally this was challenges of the pregnancy/being up with the baby all night. But the baby is mostly sleeping through the night now and the trend persists if not quite as severely as before. She's not staying up super late (not later than me) and I just have to feel there's something I should be recommending to her.... I want to help but I have my limits, and the kids need her, and I want her to have a better quality of life than this.

TL;DR: My wife seems to be really struggling to leave the couch, just constantly weary all the time. I don't know what to do.