hey emil!
My names Paige and I'm 12, and I have becker type MC. I found out when i was 8, but my mum knew since i was little. Like you, i used to get teased for not being able to do things like running ect;. It does get better though, as you learn to live with it, and hopefully you will find that people won't tease you as much now you know you have MC.
At my school, all the teachers know about me and so do the kids, however i do always feel self-conscious when walking up stairs and getting up from chairs and the floor and things.