Depression or Broken Heart?

Negative thinking makes my world go 'round when it comes to dating. It always seems that I can never find a person that makes me happy. But is this because I have yet to find the one, or is it something deeper? This sadness that I haven't been able to shake has got me feeling like maybe I have a problem, like depression. But from my research, to me it seems like depression and a broken heart are one in the same.

According to a website, symptoms of depression are listed as:
you can't sleep or you sleep to much
you can't concentrate or find that previously easy tasks are now difficult
you feel hopeless and helpless
you can't control your negative thoughts, no matter how much you try
you have lost your appetite or you can't stop eating
you are much more irritable and short-tempered than usual
you have thoughts that life is not worth living

Love can make you feel all of these things, at least I know it has made me feel this way. But when do you draw the line between being broken hearted and clinically depressed? Is it when that person has moved on and you're still sulking in your sorrows? Or maybe when you've found someone new but can't seem to trust them when they haven't given you a reason not to? I sleep my days away and feel beyond hopeless. But in the back of my head I'm thinking, "is it possible that the cure is love?"