I assume you mean 20 mg and 40 mg/day on the Pred?
A month isn't very long to take each one of these medications, as it takes that long for them, except the Pred, to even start working.
I haven't taken any of them them except gabapentin, but I do know that a month isn't really long enough to tell if that's going to do a lot or not. What was your dosage?
If you do it properly, you should work up to a therapeutic dose... for instance, when I took it, I had to work up and it took nearly a month just to get to 300 mg/day and I eventually worked up to 900 mg/day.
I've researched both Cymbalta and Plaquenil and I've read that it takes up to a month or longer before they start working, so perhaps you weren't on any of them long enough or adequate dosages for them to work. Dosages are often increased if they don't work, at first, to see if a higher dose might work...
I always research any medication I'm prescribed or offered, prior to taking it, so I'm aware of the side effects... For instance, I've read that Plaquenil can cause blurred vision and worsening skin conditions.
Your issues seem to be more related to the MCTD than to Hashimoto's.