Are these signs of anxiety?

I have a pretty good life, a roof over my head, shoes, a normal family, and some great friends. But some days I wonder if it's real. What if I just created these people in my mind to please myself? What if I'm crazy and I just don't know it? What if this is actually just a long, endless dream? I worry that no one likes me and that I have no true friends. My friends are nice and fun and I can talk to them about almost anything, but I only doubt myself. I can't trust myself. So if I can't trust myself, I can't expect myself to trust anyone else. I even cut myself once with the end of a guitar string, and the pain felt good for some reason. I couldn't stop and before I knew it I had like 20 little cuts on my arm, but i never told anyone. I'm still hoping they won't notice, but when I look at those cuts I get a strong feeling of guilt and regret. I know cutting myself Is wrong, but I don't know who I can talk to for help. Sometimes I feel so alone in the world. I don't know how other people think of me, so do I have a mental disorder too? Am I supposed to be able to tell what people are thinking? Whenever I get like this and it's bad, it's only about once every 3 months. But i still often wonder about it, I can do it calmly though. Is this anxiety?