Hola Colombiano! I was in the same situation back when I was 12, now I'm 28. When I moved to the states I noticed I didn't stutter much in English as I did in Spanish. But now that I have become accustomed to English I stutter in both languages. I believe this is due something called secondary behavior. Once we implement such behavior which in this case is another language, our body/mind will get use to it and our stuttering will be added to such behavior. Also, we speak and think fast in our native language which contributes to our disfluency. We want to keep the same pace of talking as our family and friends but you have to understand that you might need to slow it down in order to have control of your speech. You don't have to talk like a robot but teach yourself to slow it down when talking, especially on the sounds you have trouble with.