This is absolutely a real thing, and I'm going through something similar right now. I've always had above-average language skills even to the point of being pedantic, but recently I've found that I just don't want to talk using my voice. It's so much effort, especially to respond to NTs banal comments that they throw around just for the sake of making noise. I've started going semi-verbal, in which I allow myself the choice between speaking and using text to speech on my iPad, regardless of my physical ability to make speech sounds (because I do have periods when under stress or after meltdowns where I lose my words and am unable to speak even if I want to). So far it's been wonderful for my energy levels, and I intend to continue it.
Don't feel guilty for losing your speech or even just being disinterested in talking just because you're not a kid and have a history of being fully verbal. We have to decide for ourselves what will make our lives easier.
_________________
"Survival is insufficient" - Seven of Nine
Diagnosed with ASD level 1 on the 10th of April, 2014
Rediagnosed with ASD level 2 on the 4th of May, 2019
Thanks to Olympiadis for my fantastic avatar!