No one loves me at all

I am so sorry that you are feeling this way. Do you have a pet? I find that my pets keep my life worth living. The unconditional love that they give is REAL and pure.

I think you need to see a psychiatrist and a therapist and get "resources" from them. Most counties (not sure where in the world you are) have community clubhouses for Behavioral Health. It is a place to go and play bingo or color and learn life enhancing skills too.

Don't give up on yourself!

thinking it time to have a chat with a school counsellor or teacher.

How old are you, if you don't mind my asking? You sound quite young, like you're a teenager. Have you ever asked your parents whether they love you? Chances are, they do love you but some adults are appalling at showing love to anyone, even to their children. The reasons will go back to before you're born and have basically nothing to do with you. The fact that your parents sometimes tell you nice things makes me think that they do care about how you feel, but don't have the knowledge to handle a depressed, self-harming teenager. You perhaps need more time and attention than your parents have the ability to give. Are they depressed themselves? Working long hours? Tired out from other commitments?

I would go back to seeing a therapist - a different one if the last one didn't do anything for you, as it's important to have somebody you feel you like and can trust. Just talking about our problems to somebody who is genuinely listening to us can make us feel better.

That's just the start. Eventually you'll need to work on the attitudes and beliefs that lead you to being depressed in the first place, e.g. the feeling that you're a retard (I doubt that) and that people get mad at you for simple mistakes (you may be misreading their emotions; even if you are not, try not to let them disproportionately get to you. If they have no patience, that's their problem really, not yours). Oh, and don't give up studying - that's the worst thing you could do.