Feeling really down and depressed

So I'm cd27 (dpo10) of a normally 24-26 day cycle. I've been testing since cd24 and I swear I originally had a faint line but now it looks like they're all negative. I took a clear blue digital today and it said "not pregnant". It's gotten me really really down and depressed. If I'm not pregnant, why would my cycle decide to change all of a sudden? It's gotten me so confused. It's awful, it's all I can think about. I have to stop myself or I'd be testing at every hour of the day. I feel obsessed and stupid at the same time. 😢😢😢