JadeChristian1... we've had a lot of members on the forum who have Hashimoto's and have taken (or do, currently take) desiccated thyroid hormones. There's no reason not to take them, if they work best for you. Whoever told there might be a response just because they come from pigs was very incorrect...
That said, there's a good chance that your problems over the years have not, actually, been from taking the levothryoxine or Synthroid, but from not having high enough doses of either medication. Inadequate conversion of the Free T4 to the usable Free T3 or poor absorption of the med are other possibilities.
The first thing I'd suggest is that you post your current (or most recent) thyroid related test results, so we can see your status. You should have been getting tested, periodically, for Free T4, Free T3 and TSH. Once we know what those levels are, we can, then, determine whether your testing/treatment was adequate and make further suggestions as to what might help you.
If you've been off your thyroid medication for a while, I'm sure you're feeling pretty horrible by now. It's not recommended that one simply stop medication for no reason... Since you have Hashimoto's and have been on medication "for years", there's a good chance your thyroid no longer works and you can't exist for long periods without thyroid hormones.
Dear Gimel
Thank you very much for your extremely helpful advice. I shall ask the GP to test me for the FT3 and FT4 and also show him your write up. I have meanwhile stepped up the Nutri Thyroid to 3 x day and also one German manufactured supplement called AlgasanV. But like you say, I need to get the greater picture re. conversion.
You are obviously very knowledgable and I trust your advice 100%, I'm very glad I've joined this forum.
Best wishes
If you haven't been tested for the biologically active thyroid hormones, Free T3 and Free T4 ) not the same as Total T3 and T4), then you should be sure to get that done, to see where your active thyroid hormone levels are. TSH is totally inadequate as a diagnostic for thyroid, even when coupled with your Total T4 result. Free T3 is the most important because it largely regulates metabolism and many other body functions. Scientific studies have also shown that Free T3 correlated best with hypo symptoms, while Free T4 and TSH did not correlate.
Since you started having hypo symptoms shortly after going back on the Levo, this likely means that your T4 med dose is too low to get your FT4 and FT3 levels high enough to relieve symptoms, or you are not adequately converting the T4 med to T3, and your FT3 level is too low to relieve symptoms.
A good thyroid doctor will treat a hypo patient clinically by testing and adjusting Free T3 and Free T4 levels as necessary to relieve symptoms, without being constrained by resultant TSH levels. Symptom relief should be all important, not just test results. This is a good link that talks about clinical treatment.
http://hormonerestoration.com/files/ThyroidPMD.pdf
If Levo causes you to have allergic reactions, most likely due to the filler material, then one alternative would be to switch to a different brand of T4 med. There is also a fairly new one called Tirosint which is a liquid, and it is reported to be hypoallergenic. I really expect that based on your success with the NutriThyroid, you may not be adequately converting the T4 to T3 and that you will need to go to a T4/T3 combo type of thyroid med such as Armour Thyroid, or Nature Throid. I suggest these rather than the OTC thyroid supplements, just because of the reputation for greater consistency and quality. You need to be sure that you are getting a consistent dose of your thyroid meds.