Can anyone help? Having a hard time understanding

I am new here and i am really looking for anyone to help me handle and cope in a healthy manner. Im a 32 gay male & was with the same partner for almost 7 years. My ex is 8 years younger than me and lived together for 5 years. My mother was with us for the last 3 years and i was her primary caregiver. Dementia evolved and as a result both my ex and i suffered from burnout. We separated 4 months ago at which time my mother was taken into a full time care facility for dementia patients. Both my ex bf and i were able to easily recognize that our relationship was more like best friends / roommates than a partnership AFTER the fact & i was easily able to remember what i believe i want from a partner. ( for not having it with my ex and talking about it openly now ) Knowing i was in no position to become involved with another man anytime soon , i started to rebuild my life. Self esteem issues and severe trust and jelousy issues were always my underlining and i continue to keep a journal to this day , in hopes of managing those feelings. Being a person who always trusted his heart , randomly i met Brian roughly 3 weeks after my ex moved out of our house. Brian sparked a flame in me i thought long gone and i followed my heart into a new relationship. We spend every waking minute together & he is now a tenant in my house ( we essentially live together ) Brian has been seperated from his ex of 10 years roughly 1 year ago and is 26 years old. He and his ex Joe are still close friends and this only helps to fuel my insecurities. It was discussed and resolved to my satisfaction between Brian and I so i believed i could handle it. Now that you know my backstory , here is my issue. Joe was recently in a life threatening accident. He was touch and go for a while but has regained consciousness & most of his memory. He has been hospitalized for over a month and remains in care. Brian naturally was devastated by this news and has been to visit Joe several times to monitor his condition. This has of course put a strain on our relationship & i was able to get past my insecurities by being supportive 100% to the situation. Not once have i expressed my own issues as i believed it to be nessisary stress for Brian. Last week Brian saw joe for the first time conscious and speaking. Massive brain trauma posed a threat of memory loss but thankfully only small loss of memory occurred. He remembers Brian but he believed him to be younger than he actually is ( an earlier time in his life before me ) Since the accident Brian has changed. I expected this but am unable to cope with how its making me feel ( nor did i expect it ) He has become less dedicated to OUR relationship and constantly speaks about how things are with Joe. Often he will become depressed and cling to objects of importance to THEIR relationship. Sometimes he's upset or angry and its clearly because of the situation with Joe. During last weeks visit Joe remembered who Brian was and showed signs of becoming himself again. This seemed to push Brian to an emotional peak and he has been consumed with it on a daily basis. So much so that i barely recognize the man i met 4 months ago. He is emotionally and physically distant and takes no consideration for my involvement ( or lack thereof) in his life. So much focus is on Joe. He consume more alcahol than he ever used too and produces a feeling of unrest and unwantedness in me that i cannot cope with as of late. Any attempt to talk about it only aggravate matters. HOW do i wrestle with my own insecurities while maintaining support for his friendship with joe? Will he ever love me like he loved him? Does he still love him? Does he see this as a chance to start over again with Joe? Will he ever be the man i fell in love with again? Only SOME of the thoughts that plague my sleepless nights. Can anyone relate ? Has anyone experienced brain trauma and memory loss between ex's and current lovers? Can anyone give me advice for my relationship? Can ANYONE help?