2nd time period has randomly stopped?

Not my last cycle but the cycle before I had started with a light red blood and a dark goopy blood (sorry for the description just want the best answer) and then it just stopped, come my next period it was regular if not a little more heavy. 2 days ago I started with the same way with the bright blood and a little dark and randomly just stopped yesterday evening. I have been on the pill and NEVER miss one or take it late. I am 19 and have been on it 2 years, I ve noticed I ve been under stress but not sure if thats a factor of my periods randomly stopping. I plan on going to the doctor but theu can t get me in right away so I and just wanted to see someones opinion. Is it just normal for periods tp be this irregular once you re older? Because I ve never experienced this and the first time I had it happen 2 months ago I freaked and took 3 tests, all negative. Should I be worried??