I skipped a period should i be concerned?

Im 15, and usually get it every month on the 29. Then it carries over to the next month till like the 3rd or so. In April i fot it on the 29. Then it ended usaul. Then in the month of may i havent gotten it. Should i be concerned? Im worried, but havent said anything to anyone. Ive been getting periods for 2 yrs. So its awlays regular. Someone help?