My Period Tracker I Haven't Gotten My Period In A While?

I haven't gotten my period in a while? - my period tracker

I am 15 and I remember the last time my period was about 3 months. Something has happened in the last month, but it really was not my time ... Brown, it was just relief that lasted for about 3 weeks. (I had all the mood swings during this time, though) I think a time in my ipod Tracker said that the estimate if I should move, and not yet arrived. I am a little nervous, because I go four in Europe for 3 weeks, 27 June, and I would tell you so ... Is it normal that my periods are irregular?
I lost 30 pounds in the last 5 months and exercise and eat all the food orangic healthy. Had something to do with it?
Also, I think not really got a lot of stress. I think a littleSchool