I'm scared!

Hey my cycle started Dec. 15 and today I was 10 days late for my period. I took a test a week ago which made me 3 days late for my period and it was negative, today it was very faint. If it is in fact a positive then I am due sept 20th according to my app. I'm worried thought that I'm so many days past my expected period with such a faint line. Does that anything? Please respond and let me know.