The relationship between me (28F) and my boyfriend (31M) is pretty decent overall. Our communication is good for the most part, we can be very honest with each other, we respect each other and act usually very supportive of the other. We've been together for 5 years now.
One thing I cannot get behind though is the fact that he has some traits and qualities I cannot change and which will, very likely, never change. Most of our arguments are about the same topics. Often times it's about his lacking degree of emotional regulation towards inconveniences or stress in general. He frequently uses me as an 'emotional dumpster' when he wants to vent about the world and whatever happened to him that upset him (note: not all of these things are really overblown and unreasonable as my wording might make it seem). Recently this happens a lot more frequently and it's exhausting.
He's already in therapy because of depression and ADHD (already medicated). I know that emotional regulation is especially hard for people with ADHD and this is what makes this so incredibly frustrating. I'm at a point where I don't wanna hear about all these same things anymore that bother him. He's just venting about it at me, not changing anything (e.g. talk to the person at work that actually upset him) or trying to work with his emotions to not always react this hard (which again, might not even be possible). To add some extra salt to the wound: He formed a new friendship with another person at work which is all fun and giggles all the time. So basically, he comes home, tells me how much fun he's had with this person and what cool stuff they've been doing this day, and then starts to vent. It feels like I'm being served all the negativity he's built up over the day, and this person is experiencing all the fluffy joy he has to offer instead (he's a very fun and goofy guy when he's not venting and marinating in his own misery). Yes, it's honestly the first time in perhaps 10+ years I felt some sort of jealousy.
I've voiced my wish for not being used as his private therapist all the time many, maaany times. He always apologizes and wants to better himself. Never does. We also get into other discussions about the same stuff over and over again, too. Also mostly related to his ADHD (cleaning, putting some effort into planning special days like anniversaries). In general, he's apologizing all the time and I believe him but at this point I can almost predict the words that come out of his mouth every time we're having this conversation.
A part of me feels like 'well, it's the ADHD, suck it up. If you like him, YOU have to find a way to deal with all this, not the other way round'. Another part, that has a lot of old childhood trauma mixed into this emotional response, screams at me that I cannot accept my boundaries not being heard. I don't want to go into details of my backstory, let's just summarize that I've had my fair share of therapy to work through this independently. I feel stable and pretty safe in that regard. But these two backgrounds—one person with ADHD, one with former PTSD—feel like a nightmare to mix.
Is anyone out there, perhaps with the same combination in their relationship, who can perhaps offer some advice? How can I not get triggered by making the experience of 'nothing will ever change, just swallow your anger and adjust your needs' over and over? It goes heavily against what I learned back then in therapy. All of this is really sucking the light out of our relationship. The fun times get less and less, all this 'drama' is leaving me so exhausted and depressed. One part of me is slowly giving up, since it all seems so hopeless to me. Please, offer some advice.
TL;DR: ADHD boyfriend (in therapy & medicated) constantly uses me as emotional dumpster + we have the same arguments over and over to no avail. Therefore getting depressed myself since I feel like I just cannot expect any change at all + this heavily triggers some of my former trauma memories of helplessness.
Edit: Adjusted TL;DR