I started taking some Valerian and 5-HTP with my ZMA at night to help me sleep about a week back.
I've never used 5-HTP or ZMA, but I have used Valerian. I had no problems with it. It helped me drift off to sleep, feeling well refreshed the next day. I experienced no adverse effects from using it. Your headaches could possibly have come from another source.
Hope That Helps,