If you are having doubts, it's really important to take a step back and examine them. Don't just dismiss them by telling yourself that you are overthinking things. Trust your instincts.

Why is marriage off the table? When you say that there will be no more texting if you end things, does that mean that you won't text him or that he told you that he won't text you?

You mention feeling like things are good and you are good when you are with him, and that you don't feel that way when you are on your own. I'm not saying your boyfriend is like this, but there are men who will take advantage of younger women who have self-esteem issues. A 19 year age difference is a big one. I used to date men who were much older than me. In hindsight, I wish I had more thoroughly examined my attraction to older men and dated people closer to my own age.

I hope whatever you decide to do works out for you!