It made me really jitterly...uncomfortable.

I started at 50mg at bedtime, increased to 100mg at bedtime, and before
the month was out...I couldn't take it anymore.

I am however, having great response lowering pain with the light therapy.
I didn't expect that. I did it just for the oversleeping and fatigue, and winter blues/shift work changes.
I use a potent B-100 complex as an accessory to it.

SSRIs do not make MORE serotonin for you. They just prevent serotonin
from being metabolized away from the synapse.

You need B6 to make serotonin. If you are low in B6, or don't convert it
to pyridoxal (P5P) because of low B2 levels, you will fail too.
http://www.diagnose-me.com/cond/C77232.html Some 5-HTP products come with B6 added to it, already.

Essential fatty acids help too, fish oil with DHA.

Some people do well on 5-HTP and others don't. You'll have to try it.
Cymbalta is irritating because of the norepi stimulant portion. You probably didn't take it long enough for the serotonin part to kick in.

Another thing that helps with depression and anxiety is inositol. This can be used as a powder. My son is doing very well on that. I used it for a while, but after several months, it started to make me hyper. My husband still takes it tho, but not every day. 1 to 2 grams a day, mixed in juice. (has no flavor).

Another option is SAMe. I have used that since 1999, but it seems to have
lost it punch for me lately. (I am just getting OLD now). I still use 400mg each morning of that, for my arthritis.