Can having hydroxyzine in your system while using cannabis give me a scary or bad trip? could the chemicals in both be causing bad reactions together?

Yes: Both drugs cross into the brain and will effect it in different ways for each individual. Either drug could have a bad individual effect, but together you increase the chance of a reaction. The best way to know it this causes a bad reaction for you is your own experience. If it happens, don't expect it to quit if you try them together again.