I don't know what to do

Hello! I'm dating someone with SEVERE ADHD. We've been in an LDR for two years (planning on getting married next fall) and the hyperfocus stopped after we met for the first time. About half a year into the relationship.  At this time I didn't realize his ADHD could even affect our relationship. I always thought of ADHD as kids being to hyper to even sit down (I knew he was diagnosed as a child as well as his sister, who is on disability due to her ADHD not even allowing her to drive) Because there were no signs until after hyperfocusing, it never popped up in my head. Our arguments and fights have been at the least, explosive; and only getting worse. About three/four weeks ago, A friend of mine mentioned something about her husband and I was so taken aback because it was like she was talking about my SO. It finally clicked in my head that this was his ADHD and not just him being a complete asshole 24/7. Since then I've read basically every forum, book, and self help website I can get for people who are in a relationship with someone who has ADHD. It's been overwhelming and emotional. Him and I have agreed we need to get help, starting with him. He was on board and I was so relieved he realized he's a big part of all of our problems. I'll admit I have some anger issues caused from him ignoring me, forgetting anything I've ever said, not feeling loved, etc. and could do better with things, as well. Up until today he has completely agreed to get help, and wasn't denying he needed help or that anything was my fault. Today, he had a doctors appointment to get a referral to another, unrelated health issue, but most importantly his ADHD. His insurance doesn't require mental health referrals which is great. As soon as we talked after his appointment I said to find a good place near him to go. He had already argued about him REFUSING to pay attention to me because he was eating (which has never been a problem in the past, but according to him,he never talks when he eats)
And so we were both kind of irritated. This blew into a huge fight, with him basically saying he has problems but mine are worse and he's refusing to get help until 
A) I get help with my problems (nagging, and not trusting him) 
B)He wants to do it on his own time which "Will be a couple months" 

I'm so worried about our relationship because I know if he actually waits a couple months, we will definitely be on our separate ways and broken up. He's the love of my life but not feeling loved at all (especially with SEVERE abandonment issues and other issues due to being in foster care and genetic mental health diagnoses) has ruined my outlook on the relationship. I don't know what I need right now, maybe reassurance, maybe advice. I'm not sure. It just saddens me that he was so in agreement that he needed help (and eventually us getting therapy once he moved here the beginning of next year) and now he REFUSES to. I'm sorry for the word vomit, I just had to get this off my chest.