Behind knee aches

Hi there! About 7 days ago the back of my left knee started to ache. I assumed it was due to the weather because of a past injury. The next day it became more noticeable and a few days ago the other knee began to hurt as well. They both ache and hurt no matter what I do. It’s not like it’s painful, but just uncomfortable and similar to the way your body aches when you’re menstruating. It’s also kind of started to hurt in the backs of my thighs. I’ve looked it up and convinced myself I have a blood clot. I’d like to also say I’m not very active and a few days prior to them hurting I had hiked and on the second day of them hurting I had run. Is it maybe just overuse? Maybe I’m sleeping weird?