I don't use bungees/martingales, but thanks for trying to help!
It most definitely will, as I am riding tomorrow :) Thank you!
I find collection comes from even steady contact with your hands combined with a forward movement. I try not to pull but simply take a contact where I can feel the horses mouth but not pulling and meanwhile ask for a forward movingly trot. I find it easier to ask my horse to collect in the trot. If the horse isn't moving forward then they won't be likely to seek the contact you are asking of them. If they go behind the bit, soften the contact but don't fully give and ask for a bigger trot but not faster. Hopefully this helps :)