If this is a discussion about the relationship between intelligence and having a degree ...
A degree isn't a machine for making people clever. It's a qualification. Just like a City and Guilds certificate in pattern-cutting, or a Grade certificate in music, it shows that you have passed various tests, met various criteria, and reached a certain standard in something or other.
Some people have good skills in one area and not others. Some people have global skills, at a very high level. I'm very good at pattern-recognition and at baking. Though probably not good enough to win GBBO. My baking improved a lot when I was doing a lot of it, and has declined a bit since I lost the opportunity to do so much. some people are very good at the global skills needed to be a successful medic and are good at carpentry (Oh lucky them!).
I don;t think intelligence/aptitude does go off, though you might need to brush up on whatever skill set you had. I think the body-based skills are more of an issue, such as being good at yoga or singing. That said, mathematical skills are meant to decline with age - is that true, or just a myth?
Unless you have drunk vast amounts, it does seem a bit unlikely you will have actually given yourself brain damage (which seems to be what you are saying? Am I being too literal?) - that strikes me as being really, really extreme and unlikely.
You know, I think you are basically being Really Hard On Yourself. Society treats mothers, carers and Older Women like rubbish. We are assumed to have no brain, no interests, and be utterly worthless and invisible. Do Not internalise this (Very Crap) message.
You have picked up many, many skills as a parent/carer. I bet your empathy skills are a zillion times higher than when you were at university. That is a real skill, that people pay money for. (Just as a for instance.)