If you feel lonely even though you are not alone, it’s time to ask certain questions. Below I have listed some that are essential for me. The list is neither complete nor precise, but it is a start. 
It may not even be your fault if you feel lonely.

How do you rate the person in front of you?

  • Do you find them selfish? Does everything seem to revolve around this person?
  • Do they listen to you? Do they recognize the information you give them and respond to what you say, verbally or non-verbally? Or are they mainly waiting for you to stop talking so that they can continue?
  • Do they see you? Do they perceive you as a person who has their own wishes and worries? Or do they simply brush your worries aside?
  • Are they using you? Do you have the feeling that you have to perform certain tasks for this person in order to be recognized by them? Do you feel that you have to earn love? That you are an object?
  • Are they trying to control you? Does this person get emotional and unfair when you criticize their behavior? When you confront them? How does this person deal with criticism?
  • Are they trying to buy your appreciation? Do they try to buy your love? With gifts?
  • Are their analyses increasingly characterized by black-and-white thinking? What is the ratio of strength of opinion to strength of argument?
  • Does this person tell a lot of heroic stories about themselves? Do they often put themselves above other people or devalue other people? Do they often compare themselves with elites (e.g. doctors, millionaires, adventurers, artists, etc.) without being elite themselves?
  • Is envy a recurring motive to explain the adverse behavior of third parties?
  • Can they only present themselves as a great person, or are they able to make other people look good in front of others? Without belittling anyone in the process?
  • Who else does your counterpart socialize with? Do they have friends and what does the other person do to maintain those social contacts?
  • Does this person’s immediate environment consist of balanced and self-confident people or are there many people with a weak self-image or possibly depressive episodes?
  • What do you do with this information now? If the other person is generally healthy, ticking just a few boxes above, you demand a change in behaviour. What if they don‘t have the capacity to interact in a healthy manner? They may like you, but hurt you all the same. What do you do? Go away? Tough choice. Should it affect your capacity to appreciate yourself and lead a meaningful life, you‘d better left. You deserve to be happy after all.

At worst, there is no communication at eye level with such people. They put themselves above other people, control and dominate their environment and are neither capable of consensus nor criticism. Children suffer particularly because they cannot protect themselves from this. Late effects can last well into adulthood, with considerable restrictions in quality of life.

So: Surround yourself with people who see you, who listen to you and who perceive you as a person. Immerse yourself in love.