First time posting! Partner has ADHD

Hi everyone! I joined this blog earlier this year, and have been wanting to post for a while! Earlier this year, my bf was diagnosed with ADHD. I'm an MFT Trainee, and I'm the one who encouraged him to get assessed. I'm surprised it took me so long to connect the dots! 

I'm very grateful that my partner was so willing to get assessed, and I know not everyone is as open to it. I'm also very grateful that my partner was willing to take medication as well. He is still on the first medication the doctor put him on, and it has worked very well. I noticed an improvement pretty quickly. However, things are still pretty hard. 

I think the biggest issue for me right now is that we've been engaged for 3 years, and have been together for 13 years. I have a lot of anger and animosity because I feel like it took too long for him to propose, and I think it's crazy that we still aren't married. We have lived together the past 7 years, and we own a car together. I have tried to talk to him about starting a guest list, and the times I tried, he wasn't very into it at all, the conversation never goes anywhere. It makes me feel like he just doesn't want to get married, but I think the issue is his difficulty in planning. I was already parentified as a kid, so I really don't want to baby my partner and hold his hand throughout the entire wedding planing process, but I'm worried that it's the only way it will ever get done. Anyone have a similar experience?