Today

I'm so tired but I must go to school. I have three hours of economy-law today and after that I have to see the dentist. I I'm in a mood  to wear my beautiful blue dress today.

Proper tenses and structures must be used to convey right senses. 

The structures and constructions used show all this a daily routine and I guess you don't see the dentist daily.

iI hope this will be helpful to you.

Your knowledge of English is good. Keep going:-) 

Today

I'm so tired but I must go to school. I have three hours of economy-law and after ( that ) i ( I ) go to the dentist. Today, I think I'm going to wear my beautiful blue dress.

Pretty good use of English .  Keep it up !  The word I is never written as i.