I have been stabbed in the back so many times. I feel like I can't even trust anyone close to me. I don't want to get close to anyone. This is the reason I have social anxiety.
Just don't let this end up making you a loner. Sronaka you are still to young to be so guarded. Plus I'm sure there is someone that will show you eventually that it isn't a bad thing to let you guard down for them.
We used to have a saying (in the mil), 'pat on the back is a reconnaissance for a knife.' Bare this in mind and you may have some warning before it happens.