OP, I had the same problem you've been having. I'm currently in a relationship with a great guy, I had a happy childhood, I'm happy with my job (just got renewed, too), and I have a good relationship with my family. By all accounts, my life should be happy. I read books, I cook and exercise and watch TV shows that I enjoy. I write a lot.
My problem, I found out, was that I never wanted to talk about things that make me sad. Ever. Not even with the person who was causing the problem. I would bottle it up, and eventually, things would blow up, and there would be arguments where I would bring up every instance of hurt from months and years of things. It's unfair to everyone involved. It's unfair to the people I'm upset with because they'd never know that something they did was hurting me or bothering me, and they'd have no incentive to change it. It was unfair to me because I didn't feel safe talking about those things, and I felt pressured to. People expected me to tell them right then, immediately, now now now what was wrong, and I was fighting against the conditioning not to let on how badly I felt.
Maybe taking a look back would be helpful here. Try and think about situations in the past where you tried to tell someone about something that was bothering/hurting you and remember what their reaction was. I had boyfriends in the past who would always try to delay an argument until it was too late to talk about it and not feel "irrational" or like I was "still going on about that". I had boyfriends who would never even notice if I were upset, but who would expect me to listen to them tell me all of their problems. Years of this led to me feeling like I couldn't be angry or upset or bothered by things, because I'd never been given the space to do that. I'd never felt safe enough to say the things that were on my mind without someone saying I was being emotional or overreacting or irrational.
What I'm trying to get at here is that giving the monster a face, a name, a reason for being there is the first step to keeping it under control. And ultimately, that's what depression is. It's a thing that lives inside you that tries to take over every now and then. You just have to name it and try to gain some power over it. It'll still win every now and then, but at least you can try for "normal" most of the time.
