I know the feeling of drowning in tears when talking to your boyfriend about something traumatic! I did not have to do that about my stutter as I am not someone who can hide it, so he knew that the day I met him. If you are looking for some practical suggestions, you can record yourself on a video and show it to him, you can write it down on a piece of paper and read to him or give to him to read if that proves to be difficult. Honestly, even texting and explaining why you chose to do this over a text could be a good option for you! But also, it's OK to cry, if you stay together you will see each other cry a lot, so get comfortable :D I agree with what other said here, most likely he already knows and does not know what a big deal it is to you. If your relationship is as good as you think it will make you closer and make you love each other more! That always happens when we choose to be vulnerable with people we love :) I am honestly excited for you! Every time I was scared to talk to my bf about something it was 100% worth it and made us love each other more. Good luck!!!