Dang, that sounds tough. It definitely doesn't sound like he understands the issue and if it is affecting his impression of your work performance, I think something should be said. If it's a new job and you dont know him that well, have you made friends with any of the more tenured co-workers who you are open with and who might know your boss better. Maybe you can talk with them and see if they have advice on how to talk to him. I understand this may be weird as you might not want to involve other people in your "issues". But if you do have someone to talk to, maybe even asking them can be a mini practice explanation before your boss. Are you currently in therapy or go to any NSA or other support groups? They might have some good experienced advice for you? You can also talk to HR I guess but for some reason I dont like that option unless you've tried explaining to your boss and it's not working.