How Did This Happen??

So, somehow in the course of the past few months, I now find myself fully immersed in a relationship. To what extent this relationship is, I don't know (as I'm not going to be the one bringing it up and things are totally fine between us, so why rock the boat, right?). I know it sounds silly, but it feels as though I accidentally woke up one day and was suddenly part of a couple. I don't know how that happened, it just did. Now, granted, for all I know it could be totally nothing and vanish as quickly as it started, but for now I'm enjoying myself. Well, for the most part. The rest of the time I'm trying to figure out why the more I care about him, the more my mountain of insecurities keep making an appearance. Why does this happen? I'm not this weak of a person and yet I'm questioning every little thing. I'm annoying myself; my friends must be sick of me by now. Is it only going to get worse from here? Because I will not be able to stand that. I'm already sick of all the worry. I just want to enjoy the ride and have fun, not be this crazy person. How do you find your footing when navigating a relationship? I'm going to need some tips. Help!