Have you had any incident in the past where you have been cheated on or you have come across such people? even if yes, are you generalizing it? Its ok i understand you have stress and doubts but trust me you can overcome it through therapy and counseling. you have lot of negative cognition.

Feeling low, having crying spells, sleep and appetite disturbances, and difficulty in concentration and attention are some of the signs of Depression. Consult a Psychiatrist for a detailed assessment. It is likely with medication and counseling the symptoms will improve. If you are feeling suicidal or hopeless consult a Psychiatrist immediately.