What Causes Swollen Legs?

sir, oneday 3/2/2011 my leg is swolling and i go to doctor, doctor says that it is happened due to cold than gave me antibiotic but when there is not better than suggest it is phyleria. than i started phyleria medicine after 12 days i feel breathing problem. than go to appolo hospital doctor says that it is blood clot in the right leg and also it is develop inthe clot inthe lungs. than doctor treatment after seven days i am now ok. but now iam continuing medicine acitrom 3mg monday to friday and 4mg saturday and sundary at 6 pm and tonact 10 daily at 10 pm. i wear long knee cap when i go outside but leg is swelling after work inthe office day and evening. i ask to doctor about this why leg is swelling, but doctor says that it is swelling due to clot in the leg. i want to know that sweeling the leg is curable or not. i also walk daily 3 to 4 kms. exercise the leg. kindly reply than i shall be grate ful to you ok thanks.