My best friend is a married man whom I have grown deeply in love with. I enjoy making love with him but I keep feeling guilty. I have a strong drive to be around him all the time. The more I try to control my feelings for him, the more I wish to be with him. Please advise me on how best to control this urge and strong sexual feelings for him.

Most of the time such relationships are need based. You are not able to come out of this because of your emotional and sexual needs. You have to put check on your needs to come out. I know it is difficult but at the same time not impossible, provided you really want to come out. Actively try to find out suitable match and get settle down.