Hi Fjane, oh the wonders of womanhood.

Unfortunately the female reproductive system can go a bit squiffy at times, often because of a hormone imbalance. Sometimes periods disappear, sometimes they change how they present themselves. The best thing to do is consult your family doctor. There's little point trying to guess what's going on. The doc can arrange blood tests if necessary, and offer advice, maybe treatment. 

Good luck finding a solution.

regards, gamechanger