Hot flashes?

I am a 26 year old, so definitely not menopausal or peri menopausal. My period is due in 3 days (ish). Last night, I woke up and had kicked off all of the blankets and was covered in sweat. I tried laying there still in the hopes that I would cool off, but I ended up having to physically get out of bed and stand in front of a fan in the other room. I am not a sweaty sleeper (quite the opposite; I’m usually wrapped in a blanket year round).

Are hot flashes potentially an early pregnancy thing? I did have unprotected sex with my boyfriend on one of the last days of my last period about 3 weeks ago. Is it perhaps a one-off thing? Should I be worried?