I didn't notice my partner was moving on until it was too late

My girlfriend[F26] and I[M27] had been dating since our senior year or highschool, 2016. Our relationship was a net positive, but we had our ups and downs, mainly because we had moved away to a relatively small town a few states away, and we both got bored and I think we subconsciously blamed each other for it, but that's besides the point.

A little over a year ago I found myself falling into a bit of a prolonged depressive state, where I didn't have strong feelings regarding most things in life, one of which being our relationship. I didn't necessarily want it to end, but I didn't feel fulfilled. We decided to go on a break while I tried to figure out what was up.

During this period, we started sleeping in separate rooms and stopped having romantic interactions with one another. We still regularly interacted and spent time with each other, as we are really each other's only friends. This made it so I didn't notice much of a difference and kinda got used to the separation. That being said, as it continued on, I made it a point to let her know she didn't have to wait around for me. In this depressive state, I was inclined to believe that our relationship was the issue, but I also didn't see myself getting better anytime soon, which is why I suggested that.

Within the last month or two, I had made some good progress with a new therapist, and I have been coming to terms with some accountability issues and other fun things. I had also noticed my gf being much more distant, and it started to click that she was losing interest in me, and no longer waiting around. This realization made it so all of the suppressed emotions from the last year hit me like a bus, and all of a sudden I was terrified to lose her.

Just today, I wrote her a letter, talking about all that I have come to terms with in therapy, and that I have been realizing what was on the line to lose. I ended it by saying that I would love to see how I can continue to learn and grow with her by my side if she'd be willing. She dropped the bombshell that she is not interested in pursuing a relationship with me anymore, and it felt like I was hit over the head with something. I hadn't realized she was moving on bc we were still spending so much time together, and when I started to feel like myself again I was shocked to find out that she no longer had romantic feelings for me.

I've been spiraling out of control a bit, as I wasn't anticipating to feel all of these rather intense feelings. I am upset that I didn't notice it. I'm frustrated that I initiated the separation in the first place. I'm sad that she's not here for me when I finally felt like I was getting better. I told her in the letter that I would understand and respect it if she chose to not pursue a relationship, but when reality hit, I became much more emotional. I don't have a good relationship with my family, and I don't have any friends, be it where I live now or back home. I can hardly afford to live on my own, and I have no way to move anywhere else. I'm quite scared for the future to be honest.

My biggest issue is that there isn't an apparent reason for the break up. Neither of us did anything wrong, I just fell into a depressive state, and she moved on. Part of me is upset that she didn't stand by my side and help me through the funk, but part of me is happy she was able to move on and not get stuck with me. I'm just incredibly frustrated because I'm ready and willing to fight for my relationship of what would be almost 10 years, but she checked out already, so there is nothing I can do.

Thank you if you read this far, apologies for the wall of text.