I developed antibodies in my blood. Why?

This may be normal. Antibodies are part of immune system's defense against infection. Without antibodies you would not survive. They may be involved in some diseases like rheumatic fever or rheumatoid arthritis, in which they may be harmful rather than helpful.
Auto-antibodies. Our immune system makes new antibodies all the time in order to fight infections. Autoantibodies are proteins made by the immune system that target the body’s tissues. Normally autoantibodies are routinely eliminated by the immune system’s self-regulatory process. Through a process we don't really understand, sometimes these autoantibodies aren't properly eliminated, leading to disease.