You're doing great Ben :)
Keep it up and we are here for you! x
I used to be like your boyfriend. Worked hard, played hard. Didn't drink very much. By 30 a leaking guy syndrome / celiacs caused a autoimmune response to gliadin that then attacked the similar thyroxin molecule so doctors destroyed my thyroid. Then they put me on drugs which had nothing to do with human chemistry and i got deathly ill. still longer on the SAD diet and my celiacs began attacking my liver and then i got horrific symptoms.
I then tried to eat "paleo" for a year and got sicker. Finally I woke up to 80:10;10 although I struggle to stay on it.
be grateful you woke up so young and that the info is out there now. and rest assured... maybe not this decade, but eventually ... his diet and ways will come crashing down on him.
honestly, I do NOT think a "good" partner would leave because of that. a "good" partner might be initially concerned for your well being, and make sure you're being healthy and knowing what you're doing, but NOT be "embarrassed" by your health!
health is so important. sometimes, it's even more important than keeping relationships with those who don't care about you (and your life!) maybe this is a good thing? maybe this is a sign? you'll find someone supportive!
if not, and you stay together, maybe he'll come around and help you in your journey? it's all a bunch of ifs and maybes, but that's better than "no"!