Suddenly a long cycle, anyone have experience with that??

Hi everyone!

I'm kind of worried about something....
Last month I thought I was pregnant. I was 11 days late but all the tests stayed negative, so I got my period anyway.
That meant I suddenly had a cycle of 40 days....
But anyway, unfortunately, the next round...
Now I'm 5 days late again but the tests are still negative.
I've always had a 28-day cycle, so I find this so weird....
Has anyone else experienced something like this or does anyone know how this can happen??

I'm not really focusing on it too much, so I'm really wondering why I suddenly have such a long cycle, or could I be pregnant this round but just not be able to test yet.......