Actually, a purely selfish desire to use people, Moral Egoism, is not "basic psychology". It is, in fact, a sign that something is fundamentally wrong with the individual in question- like psychosis, sociopathy, narcissism, etc.. Or Codependency. Codependency is a little different though, it's a case of first giving WAY too much totally selflessly. Then, you turn around and want the recipient to return the favor, and they don't, so you get mad at them...
But seriously. Most people actually do derive pleasure from helping others. Mirror Neurons are no doubt part of this- we feel what others feel. Our brains are designed to be empathetic. While you can argue that everyone is still selfish, you are missing the point, and I would suggest you look for James Rachel's response to moral/psychological egoism. The theory is infantile and doesn't ultimately work.
Seriously, dude. Take a break from people, that's fine. But don't give up entirely, there are good people. (I should also remark that you on some level believe that. Otherwise, why on earth would you be asking for advice here? I certainly gain nothing from helping you. I will probably never meet you, and I don't even know your username. Strange as it sounds, I just want to help you. That's why I'm here.)
Cleanse your aura and chakras, heal, learn(psychology and spirituality) do power meditations, and you'll be surprised when good people start coming into your life. What you put out is what you get back. If all you think of people is that they are going to mistreat and use you, first, someone who WON'T mistreat you won't want anything to do with you. Why deal with unjust or unmerited suspicion all the time? Second, you may find you want nothing to do with them. Look up codependency. You may have it, and that may be why you keep running into these problems.
Do you ever go too far out of your way to help someone? Do you ever find yourself helping someone against your own will? Even when they haven't asked for it?
If so, you're surfing the Rescue/Persecute/Victim triangle.
It does get better, but look to yourself first. Good luck!
HAIL SATAN!