Cycle lengths

I’m 19 about to turn 20 and I’ve been getting my period since I was 13. My cycle used to be 35 days long with a really heavy period but it’s changed to 28 days with a much lighter period. My period is still 5 days but my cycle hasn’t changed like this since I first started getting my cycle. By now it should be normal and come when it always has right? Has anyone else experienced this.