Is this sentence ambiguous or not?
Solution 1:
The sentence is referring to one activity, with the body in a position, and with a feeling that the person is having while doing it.
The activity is reading. The position is "sitting" or "seated". (In England they would even say "you could be sat here".) The feeling is one of these: depression, anxiety, or discouragement.
It may be tricky because of the list of feelings at the end of the sentence, but to me it is pretty clear that the sentence is meant to be understood as: (Sitting here) and (reading) and (feeling [x or y or z])
Hope this helps! Elie