Sorry you had this experience!How much tea tree oil did you use? I use only one or two drops. I wonder if mixing two very strong oils, oregano and tea tree, is a bit much....
In any case, your body is telling you that it does not like it, so you made a wise choice. I used to have similar exoeriences with the olive oil and lemon juice mix for liver flushing, until I switched to a different oil and then was fine.