Why do people not say their boundaries early on and how to prevent situations like these in the future? And could I possibly fix it?

I had untreated ADHD at that time, and a lot of negativity in my life. Never learned a proper way to cope with my emotions, but never been in an actual relationship, so didn’t even know I’m capable of doing… well, this.

Met this guy and he was incredibly loving. He was open to hearing all of my problems, was understanding and knew change required patience. He also knew what he was going into, I made it clear. He offered help, and oh boy that’s where it started… Basically became my therapist and enabled emotional dumping. Fun.

I did ask if it bothered him. No, he didn’t mind, that’s what relationships are for, he loved me so so much, he’d never leave me for that and believed we can both work together on my issues. So I believed him and did this more and more.

After 3 months of dating, he suddenly decided we can’t go on like that. He’s exhausted. I understood but felt a little betrayed. I’d try to do it less and less, but found myself struggling with changing a newly ingrained “pleasurable” habit, and ADHD didn’t help. Moreover, our whole relationship depended on me stopping it immediately, which caused sooo much anxiety, things only turned worse and worse.

He’s also stopped all the affection and intimacy, I saw the resentment growing. I tried so much, but it just wasn’t enough. Did start meds and later therapy. He broke up with me anyway (amicably).

**What I don’t understand is, what was all the “love” and what he said before for? Did he not know it was bothering him earlier? Did he not know it would bother him from the beginning (he later said he’s ran out of patience with exes before and didn’t like people who constantly complained, thanks for letting me know that… at the end). Couldn’t he just kindly set a boundary before he’d felt so drained? With my friends I know I shouldn’t discuss certain things and it works.**

I feel like I should predict everything, know better and it’s totally my fault. Just with 0 relationship experience and him encouraging it, I seriously didn’t think much of it at that time. Why couldn’t I stop……………

What hurts the most is the sudden change, downfall and feeling like we could’ve had something beautiful, but it was just cut short because… yeah. I keep having an urge to fix this, and it’s additionally tormenting me. What can I do better aside from continuing therapy?