Play with your body as you're doing this. If you're a boy, edge a few times and if you're a girl, really start working on the clit.
Enjoy this moments and have fun. Don't forget however to push yourself harder. And in order to become a real slut, you will have to do this often. To get it to actually work, you should do it at least twice a week, to become really good at it it's best to practice daily. If you don't have enough bananas, each time you get the chance, try to deepthroat yourself using your hands, your toothbrush, whatever you have.
It takes some time, but you must get that gag reflex under control. And it's all about practice.