I had an ultrasound for blood clots on friday. test came back negative. last night while sleeping i got a sharp pain in my leg like a cramp. is it possible that i got a blood clot over the last 6 days if i've been smoking? i'm not a regular smoker

Anything is possible: But a recent ultrasound being negative would make this very very unlikely. Blood clots in the leg cause swelling, persistent pain, especially when walking/ bearing weight. Often times there is redness and warmth affecting the leg as well. Night-time leg cramps are not associated with these clots often. Women on oral / implant contraceptives have a greater risk of blood clots while smoking.

DDimer: Studies show that people with injury to their legs, hypercoaguable states (more prone to forming clots), or those who have been sedentary (immobility) are more likely to have a blood clot. Wells criteria are clinical criteria that include recent immobility, cancer, and other factors in determining the probability. You need a full history and physical, however, a DDimer test can be useful.