Try to release the reins quite a bit more.. in english you are "on the bit", western you are not.
In western, the horse carries itself.. you shouldn't be pulling on their mouths at all.
In western it's all about "long" and "low". You want their neck to be long, and really low.
To get them to lower their head, lower your hands down, tug gently with the left hand, then the right, then the left, then right.. sort of like a half-halt, but with one hand instead of 2.
Slowly, the horse's head will edge down :)
Lean back, and sit deep ;)
Looks like you had fun!