To me it sounds like maybe you aren't doing what you really enjoy in life.

Go out and do things that you want. If your boyfriend isn't making you happy, he's not than.

Your mind needs exercise as much as our bodies do. You know what happy feels like, but you're not feeling it, well practice happiness. How? By doing the things you enjoy, at least once a day.

It will still creep in, because its normal, but just keep doing things that do make you happy and you'll find yourself a happier person eventually.