Why are my dry?

I have been having dry for past month or so, I don't think I'm pregnant since I did not have , but I haven't had my period for about 4 months and I'm 14 :S And before my period cycle was completely normal, I would know exactly when I would get my period..etc. And the weather is now very nice since it's spring ... I have no clue why this is happening, there are just a few flakes..any reasons?