I've been 4 days with pain and tightness behind my knee and calf, the pain is mostly when i stand up and walk, there's no redness, no warmth. i have no idea where that came from since i have no injury. i'm a little scared, can this be a dvt?

A DVT can happen without any symptoms so it would need to be ruled out by ultrasound. Did you have any period of inactivity-like a long car ride, plane ride, etc.? That is how clots typically form. But, you can ask your doctor to do an ultrasound to rule out a clot and it is a non-invasive test. If it is a clot, you can be treated with oral medicine. If it is not a clot, you can see your doctor.