Missed period

This may not directly relate to this group, but hopefully someone else has experienced this.

So the first day of my last period was on January 17. Im on cycle day like 50 or so. I have never had a late or missed period. I took four pregnancy tests, the last one on March 2nd and they were all negative. I have anxiety about going to the doctor because I don’t think it’s pregnancy and i’m worried about what the true cause could be. If any of you have had a missed period not due to pregnancy or anything that may help me out i’d love to hear some more about it!