Good for you for getting off the Vicodin.
The fact that you've been on Ativan for "a few months" and are experiencing horrible anxiety with panic attacks tells me the Ativan is no longer working for you. You need to get back with your doctor and discuss these issues.
I'm afraid I know nothing about this 5htp stuff, but what I DO know is that sometimes the result of mixing these things can be disasterous. Most of us believe that just because something is "natural" it can't hurt us, but that is a myth and SOME combinations can be lethal. NEVER add any sort of natural remedy, be it herbal or supplemental to your meds without first talking to your doctor.
Peace
Greenlydia