(This was yesterday) I told my ex i liked him and he seemed interested. I called him to explain my interest but he never answered or returned my call, what should I do?

He's given you your answer by not returning your call.  He may just not have wanted to hurt your feelings face to face but if he were interested at all he would have called you back pronto.

It's often difficult when we still have feelings for an ex but don't try again to contact him or even talk to him other than casually, you're only going to get hurt if he feels you're pursuing him.