10 day late period... Scared?

I'm really worried because my period is now 10 days late and I know I'm not pregnant. About a month ago, I was on dome strong antibiotics for an infection, but have stopped using them a few weeks ago. Maybe this could be linked? I'm also experiencing some stomach pain, but I cant pinpoint where to... It varies from my lower stomach to my just left diagonally upwards to my bellybutton. Anyone fill me in? I'm 16 btw...