How about a course in anger management, so you can feel stressed without fighting with people?
The first thing to realize in the friendship department is that you are playing out an inner drama and pasting it on other people. You have undigested feelings of anger or of feeling unloved, and you project these feelings onto your potential friends. Anything you can read about "shadow" material (from psychologist Carl Jung and Jungian psychologists) should be helpful.
Let's start with Mars retrograde in the 11th house of friends, opposite your sun. The sun is your identity or sense of who you are to yourself. Mars is your natural assertiveness, aggression, and sense of masculinity. A planet opposite the sun tends to show up as "not me", and often as someone else who seemingly embodies that planet's negative characteristics. Then with Mars retrograde, all of your natural aggression is turned inward. This makes you feel that other males (Mars) dislike you (sun) and you beat yourself up over it (retrograde Mars). Are you your own worst critic?
With the sun in Cancer, you probably tend to retreat into your shell when your feelings are hurt, snapping your claws occasionally.
Your sun-Mercury also make a wide square to Pluto. People with this aspect were often bullied as children, and they grow up learning to mistrust people. They start to see the world as a "zero-sum game" in which any difference of opinions results in a "dominate or be dominated" mentality. Any yielding to somebody else is seen as a defeat of sorts, and personal relationships get construed as contests of wills.
There is a more empowering use of these aspects, but you will have to get out your "poor me" model to do it. Mars also rules athletes, so any kind of group sport that strenthens your Mars in a constructive way should be helpful. With mars retrograde, concentrate on your "inner game", be it pick-up basketball or climbing Mount Rainier. With your sun in the 6th house of health, think of an athletic activity or two as supporting your physical fitness.
And please don't say you don't like any kind of sports activity or you don't want to join a group activity. The point of astrological self-awareness is to strengthen those astro-muscles that have been giving you difficulty.
Pluto at its finest is all about ongoing personal transformation. Think of your sense of self as being constantly pressed by the cosmos to grow and evolve as a human being. As a human being, let alone one with sun-Mercury square Pluto, you are not a set of static personality traits, such as "eccentric." The crab on the beach periodically sheds its shell so that it can grow. While this period makes it feel unprotected and vulnerable, this process is vital to its survival.
Incidentally, your chart also has a lot of cool stuff in it. With Neptune trine Venus, you probably have a rich imaginative life, and you can convey this through some form of art, be it music, painting, writing, &c. With Jupiter trine sun and several planets plus your MC in Sagittarius, you have the ability to think philosophically and to expand your mental horizons.