There may be something that you did or does that makes him lack the interest in you. Change your wardrobe, make your hair, do some makeup and you can also break the friendship barrier. You should also let him know that you are still interested in him.
If he has a girlfriend then you need to move on hate to say that but it is the truth.. There is no since in just waiting your wasting your time they could last a long time together and you would be just sitting there, but yeah it's best to find someone else that is single and that you think you would be good with there are plenty of others out there looking for someone that aren't with someone since he has moved on just forget him. sorry