Pain in lowet leg goes away then come back blood clot or no?

Only way to. Know for sure is with a test called venous duplex doppler ultrasound. If you do have a clot, it can break off and travel to lungs, a condition called pulmonary embolism. This is a serious condition, could be fatal. Treatment is immediate anticoagulation, so get to a doctor if there is any question of blood clot, or deep vein thrombophlebitis.