I think if you're having issues on where the haunches are, then you don't have enough forward. This assumes you aren't accidentally cueing the horse to move it's haunches one direction or the other.
Anyway, I can't tell where the hip is if it's only off by just a slight amount. It's the other stuff that feels "off" that cues you in on there being a straightness issue. You can feel it in the reins sometimes (horse is heavier on one rein then the other), you can feel it in the relative power that is coming up through the horse's back (less power with same forward then the horse is not straight), and I can feel it in how my hips sit on the horse (it shoves my weight to one side so that it feels like I can't put my weight on that seat bone without consciously shoving it there).
Wiggly is training. Consistently off one direction is strength and suppleness issues. If it's not just wiggly (goes both sides consistently), then ask your instructor for exercises to help develop the carrying power, strength, of the leg. Like haunches-in, shoulder-fore, circles, etc. Then use those in your daily riding to help develop the horse's weak side until both legs are able to carry you equally. I did haunches left for 4 months straight because my horse's left hind was so weak. We never even touched haunches right that entire time because that leg was already strong from carrying all her weight for years.
P.s. You have a pretty condescending trainer to say "can't you feel that". If you could, then you would've fixed it or asked about it, right? If I ever have one talk to me like that I'd "accidentally" smack her with the whip next time around the arena. ;)