Now you are expressing the idea that you feel depressed but only sometimes. You are not able to concentrate on studies also,. There are many people like you who can't believe in others and who are a closed book as they don't easily let people inside their world. Are you feeling worthlessness also?. Visit to a psychologist will help in determining your personality types or whether you are having underlying depression.

Hello dear, staying apart from family's security, love and affection is challenging in itself. Along with that your difficulty in maintaining deeper meaning relationships can be quite disruptive. Howsoever, you haven't mentioned whether this is your general nature or a recent change after some relationship issue, which would have been helpful in understanding things better. But right now what you need to do is try not staying alone, go out with friends and colleagues, have meals with them and engage in simpler communications about studies etc rather than conversing about your personal history & difficulties(which might make you uncomfortable). With time, you shall develop comfort and trust in some of these relations and then, you can decide about future of such relationships. That said, you should also consult a psychotherapist for figuring out the roots of such insecurities and means of handling them better. Hope this helps, good luck!