Wierd lag

im making a game that is going to be a little cpu intensive, however the lag im getting now comes once every few frames, and doesnt even out, the framerate becomes a pattern of normal rate and then a drop

30 30 30 30 30 15 30 30 30

and it will keep doing that over and over again.
im not sure if this is my poor computer, or just real lag. can you guys start the game and see if you get any lag
a red circle will appear in the bottom left corner if you do, thanks.