I think I'm depressed

I keep crying for no reason. I keep thinking my boyfriend is cheating on me when he's shown me he isn't and he doesn't hide anything yet I still have this gut feeling and idea in my mind that he is. I cry almost everyday and I just feel alone. I've never been like this before. This past week I've barely eaten, probably one meal a day (I have no appetite). I just need a place to vent and I'm sorry if this is the wrong place.