How would you describe the feeling & have YOU felt it before?

Two options: Either you truly care for him and really think he should be doing better, or you are in DENIAL (Don't Even know I Am Lying) about deeper feelings and are jealous. Let me ask you a couple questions.
When you were regularly interacting, did you look forward to seeing him more than anyone else? If so, that is emotional attachment which is one sign of what comes to be known as the emotional love.
Could you see yourself with him ten years from now, as more than friends? If not, is that a rational decision or intuitive. If it is rational, you can figure out why and explain that evaluation. If it is intuitive, it is hard, if not impossible to explain. If the answer was intuitive, it is probably accurate. If it is rational, it very well may not be. In the rational decision scenario, your lack of interest may be based on your historical training regarding what was expected of you, or what you wanted to expect for yourself. Either way, those expectations are unhealthy and you need to seek out their source before you pursue any long term relationship, if you want it to be fulfilling to the person God made you to be, in a healthy way.
Barring these being able to determine the truth, try going out with him and see what happens. It could be you bailed because you knew, intuitively that there were possibilities that wouldn't fit into your plans, or the plans someone else had for you. In either case, it is healthier to seek out, and process, the source before you react, rather than respond to the situation.

It seems that you do like him more than a friend. You seem to become jealous when he is th with other girls.