I'm sad that I'm pretty sure I caused my parents divorce
Are you really sure? Why would you think that?
I think my mom was pretty much bored with marriage. She is mature enough to realize it can't fulfill her but she still stayed there for my sake.
That's good that you can empathize with your mom, but it's a mistake to think you're responsible. She was the adult when she decided to get married. She is responsible to going ahead with a major life decision without thinking through all the consequences.
Maybe I was a bad kid.
No, don't blame yourself for it all! I'm sure you are a joy to both of your parents, and their falling out is between them, and not you. I believe you should just try to support them all you can so they are not alone.