I have been through the same. I am 33 now and I was diagnosed with Hashimoto when I was 28. I am still managing the whole situation as best as I can. Today I am physically more fit that I even was in my entire life. Although I have many sessions of unexplained memory loss and brain fog.
The funny thing is that if you have one autoimmune disease, it is highly likely that sooner or later you will also encounter another one. I was diagnosed with three. Including one affecting my eyes pretty badly.
The way I am managing it all is by
1. making sure my adrenal does not deplete(went through a super adrenal crash last year)
2. good dental hygiene(it does help massively)
3. avoid sugar, refined carbs, alcohol.
4. Probiotic natural Yogurt and apple cider vinegar seems to keep my system happy, milk makes things worse.
5. B-complex and Vitamin - D on a regular basis.
point 3 and 4 are to ensure that my gut is maintained well.
The important thing is to make sure that you try to take good care of your adrenal gland and pituitary , because they tends to overwork to compensate the malfunctioning organ that is under attack at the time.
The longer I continue my unrefined diet, good sleep cycle and avoid stress, the more my body heals.
I used to be quite a sharp minded computer scientist, now that sharpness comes and goes, other times there is fog, which is not very nice :-) But I have hope that eventually I will be better, I am already much better than last few years :-)