What are your symptoms? Do you have current labs including thyroid panel, cbc w/ dif, and ana?
I suffer from Hashi's but I see a rheumatologist because I have extremely high ANA. My rheumatologist is watching me for Lupus (which can cause Hashi's) and told me that if I develop Lupus that the many symptoms would come on quickly and in extreme. The labs would also look very much different. One example is the wbc. Mine is always high or high-normal. He told me that if I develop Lupus it will drop to 3 or 4 thousand instead of the 10 or 13 thousand that it runs now.
Of course there are many other indicators in your labs but the point is that you obviously feel much worse suddenly and don't know why.
If you could share more about what you're going through then maybe someone with more experience could also lend their expertise.
Hope this helps,