It's their fault or is it mine?

People around me dont know how I feel half the time. They are oblivious to the fact that I'm hurting on the inside and hurting myself on the outside. I'm the good friend that listens to their problems and secrets and keeps it to myself. But I'm also the friend that never gets asked about my problems or feelings. I'm the friend that gets left out when the others go on ''double dates'' or whatever just because they feel sorry for me since i dont have my ''someone special''. It makes me mad that they don't see this. They're completely unaware. I might as well be wearing a mask on my face and they still wouldnt be able to tell that something is different. But maybe it's also my fault for never telling them.