Are these periods or just my body preparing itself?

Ok so I'm 14 and a freshman in highschool. Ever since seventh grade I have had "false alarm" periods that are sometimes blood, sometimes brown discharge and the first time it had clumps, but that hasn't happened for nearly 2 years. I started running at the end of seventh grade and run all the time. They last a day, sometimes a day and a half and it's VERY VERY light. Like a panti-liners not enough but a pad is too much. They are irregular, sometimes around once a month, sometimes 3 months and sometimes I can get it one a week for a few weeks. WHAT THE HECK!?!?! I just want to know if it's a period. Thankss :D