Yes, it COULD be the fact that you stopped taking SJW. This is just an educated guess since the antidepressant compund in SJW has not been isolated so we don't know if that has withdrawal symptoms
if stopped suddenly but I think this should be a ok enough guess.
It could also be due to unresolved pain symptoms and hence if the pain is chronic and sub clinical you would probably not feel it so severe to go for pain killers but would be so irritating as to make you feel irritable and angry and moody....here I speak both from personal experience of chronic pain
and as a professional.
I would suggest you check out with your doctor first about interactions of SJW with your current drugs. If you are a female, then we know for sure that it interacts with the pill. There may be other unknown interactions also.
Hope this helps.