Hi Holi!
I've also read -in one online source only- that B-6 and 5-HTP should not be taken together. However, the reverse is actually true. Vitamin B-6 is required in the process of converting the 5-HTP to serotonin, so it is beneficial to take a Vitamin B-6 or B-complex supplement with the 5-HTP. (Other legitimate sources can be found online which support that statement).
As for me, over a 2 wks period, I had slowly tapered down my Effexor dosage to half of what I was originally taking. However, I was getting SICK of sleeping 9-10 hrs and feeling like I needed to go another 2... so one morning last wk, I got mad and flushed the rest of my Effexor pills. I began taking the 5-HTP immediately and I've not had any symptoms, except for some hot flashes that went away by the time I realized what they were. If you decide to try it, it's important to completely stop taking the Paxil before you do.
I've taken St John's Wort and didn't notice any effect at all unfortunately. But we are all unique, so don't let that discourage you if you're interested in it. It's unlikely that it would cause weight gain. I've read that St John's wort and 5-HTP often function very well together. It must be in the system for about 2 wks to work.
There are certain drugs and herbs that St John's wort does interact with. So just in case, and as you may already know, there are several websites that have drug interaction checkers on them.
Hope this helps - let us know how it goes!
Good luck!

Windy