Hi Mary...
It worries me that you have read a lot of the wrong things on the Internet. The wrong word spreads like wild fire and can - and clearly does - scare the crap out of people. Not to put other people down, but both Hat and myself are qualified in our respective neurological fields, so what we say tends to be the truth. Hat also has nearly 7 years worth of this forum behind him of people going through Cymbalta withdrawal. Take a deep breath... relax... the chances of your brain being "broken" as a result of reinstating/updosing Cymbalta is that slim that after 10,000-odd people we have not heard of it.
I do think you should give the 10mg a little while longer if you can, and then go to 15mg if you find no benefit... but this will take time and you will be getting the start-up effects that you once got (potentially worse) when you started the Cymbalta. The fact that you are feeling it worse is the subject of kindling. But this is a very controversial subject with very little evidence backed up by peer-reviewed research.
As I said before, you brain has been pulled back and forth in directions and the upshot is EXACTLY what you are feeling. The chemistry in your head had only just started to recalibrate, so by putting the meds back in again is going to have confused what was going on. It is frustrating, and going through my withdrawal whilst trying to continue my research was a nightmare. I questioned whether I would be able to continue in thinking my brain will have suffered just like you. But here I am still going.
I really feel for you, but you need to understand that the brain is perfectly capable of changing to suit whatever is thrown at it, but it is the slowest organ to heal because it is so complex. It is not as simple as a cut on your finger, or even a broken arm. But the bottom line is... your body heals, and that includes the brain. Research into neuroplasticity has gone a long way to showing us that the brain cannot "forget" how to heal... sure it can appear to have unlearnt something, but its ability to learn never diminishes.
Feel free to continue to ask questions as it will help you, but take solace in knowing that what you are told here is the truth. If we are ever unsure of something, we will tell you... and then we find the answers!
Regarding the valium, if you feel you need this dose, then by all means take it, but do not take it from habit. Valium is fine used on an as and when basis. Also remember that valium - like all benzos - have their own withdrawal, and must be done very gradually assuming you have been taking it continuously for 2-3 months.
IUN