About my past.

I am from and was born in Chiapas. When I was 11 years old I went to middle school. I was a good student and made good grades. The best things in my middle school were the friends and one girl, her name was Dulce and she liked me. What subjects didn't I like? Ummmm, I believe I did not like math but now I like it very much. When I was a young I used to watch cartoons and play soccer with my friends, now I'm follow seeing cartoons but I dont' have time to play soccer.
As for English, I am now, for the time, seriously studying English.

Gracias por leerme. Saludos desde México.

*"I'm following seeing cartoons" I could not correct this as I am not certain what it is you're trying to say. Everything thing else was understandable, just needed some grammatical tweaking. 

I removed some contractions, I'm, didn't, etc. Not really incorrect but you don't want to use them all the time. An introduction is a bit formal so less contractions sound better. 

Still better than my Spanish! :)