Damn, that sucks a lot. I feel for you.

I think it's normal after a lot of bad relationships to have regrets about the opportunities you passed up, or staying with somebody so long and not seeing the signs of them being disingenuous or sometimes downright terrible. Wasting part of your life. You really are not alone. Lots of people have that feeling to some degree or another.

I think that dating is the process of learning a bunch of relationship skills, and once you have enough relationship skills, you can put them all together and have a successful relationship that lasts forever. One of the skills that is tougher to develop is the ability to see when you should break up with your partner (or often should have broken up with your ex). When you don't have much dating experience, sometimes you only realize it after the fact when the relationship ends and you put the warning signs together. As you get more experience, sometimes you can start to see problems coming down the road in advance and hit the eject button.

So, this is your experience. Reflect on it, and try to learn something from it. I bet if you had to do things over again, you wouldn't want your relationship to be secret for so long. You probably wouldn't want it to be so chaste for so long. You wouldn't put up with so many unfulfilling life moments. You would want a higher level of intimacy in general. And if you learn those things it doesn't suck any less, but it makes it so that the time you spent together wasn't a waste. It makes it so that your next relationship can be a lot more fulfilling, and so that it can hurt a little less if/when it fails.

And if you string enough of those experiences together, eventually you have enough relationship skills, you learn enough about yourself, and what you need from a partner, and what you want your relationship to be like...and you can just put it all together and have pretty much exactly what you want.

All of that is to say, you are not alone, and you are not stupid. Stuff like this can happen to anyone, especially when you don't have dating experience.

For now, lean on people who you know you can trust not to be talking about this. Could be a very discrete family member or friend. It's very hard to go through these things alone. You should also try making an appointment to talk to a counsellor. That is extra nice because you know they will keep your privacy, and they are literally trained in how to handle emotions and stuff. It's a doctor for exactly what you are going through.

In the coming days, let yourself be sad, but don't let yourself drown in sorrow. Feel your feelings, acknowledge them, and keep living your life (to some degree) while you process them. Make yourself eat some food even if you're not hungry. Go for a walk even if you don't want to. Hang out with your friends (ideally friends who are aware of your situation), and make yourself part of the world. If you feel like shit, don't be too hard on yourself. There is a reason there are so many songs about breakups. They are difficult. Especially ones like yours.

Over time, you will still feel down or sad, but it will start to ease up in intensity, and the time between feeling the worst of it will start to grow. Eventually it starts to fade into the background and you begin to feel like your old self in spots. That continues as you process your feelings until eventually you feel relatively unburdened by your past and are officially "over it". Time will help. Loved ones will help. Stay away from drugs and alcohol. Make some goals for yourself. Do some stuff. Let yourself be sad. You'll get through it.