Bloody hell - that is a seriously fast withdrawal. I am shocked that you haven't had anything worse as a result - so don't be too surprised if something else comes along in the next few days.
St, John's wort will take a while to build up in your system, so don't expect miracles from day one. It is different from SSRI's obvously, but it still works on the same serotonin receptors in the brain which need time to react to the stuff.
Also heed Hat's note that it also has something of a withdrawal, but if you get through what your doctor has done in the last few weeks on your previous meds, then it will for sure not post a problem!