Period coming when it wants to...

Batisha
Okay I'm new to this "period talk"... But that's not the point. 
I got my period when I was 12 years old at the end of the month ( I don't exactly remember the date) but it was like 28th and every month I would get it that exact date. 
Now I'm 16 years old and I'm not sure when and why but the date of my period comes when ever it like, and I hate it because I don't know when it's going to come its like playing duck duck goose! I try to look out for signals but sometimes they change and go away before my period comes 
 Does this happens to any one? I believe this all started when I was 14 I'm not sure. And I have read about irregular period some people don't have a cycle of 28. But I don't think it that pleas help me or give me some information.