At the end of your post you write that you’re afraid of opening up to people after all your bad relationships and that you lack the courage to do so. Maybe I can help you with that.
Courage is tied to seeing the world as it really is and knowing yourself. It doesn’t sound like anyone in any of your relationships has abused you, so much as they’ve disappointed you. Welcome to reality. My suggestion is to know yourself better than you do now. Instead of plunging feet first, stop and analyze for a while, what it is you want from your life and from a relationship. Figure out what you have to offer someone else, and like a ven diagram, what you want and what you offer, will overlap in a sliver of who is right for you and vice verse.
So stop looking at the world, and start looking in the mirror. Then jump feet first only after you’ve chosen someone who fits your criterion for a good partner, and for whom you fit theirs.