Urgent! Please HELP! My husband has swelling, pain, and rash looking redness on his leg?!?

Im worried it could be DVT... but im not sure... it goes and comes every couple of months.. fever every time of aprox 102... he is aprox 400lbs 6'3 25yrs old.... he is able to walk on it.... i suppose its brought on by exertion .... antibiotics usually do the trick after a few days... he usually gets a pain and knows the fever will follow... im worried it could be a blood clot so please help! any advice will do.