Skipped period. Is this Normal?

I’m 18 and have had my period since I was 13 and never skipped a period before except when I first got it... I’ve been getting my period regularly for a long time and had my period last month... I know for sure I am not pregnant because I have not had sex for the last 2 months... but I’m late by 4 days now and I’m usually on time... has this ever happened to anyone?

Nothing in my lifestyle has really changed besides I lost some weight but not an unnormal amount, I don’t feel stressed, and I’m eating normal.

Is this normal or should I be concerned? And any tips on how to kick start my period to get it?