Exhaustion.... Early pregnancy sign?

Last week I had what felt like the flu. In case this is the month I get my BFP I didn't take any medicine. Now I'm feeling a lot better but after work today I passed out. I mean out cold deep sleep and it was only 6pm!! I've never felt more drained! I'm a teacher so I'm always tired but never like this. I'm currently 8 DPO. I've never felt like this before. I can barely keep my eyes open. Anyone else experience this level of exhaustion then get a BFP??