I was adopted. Big deal. So are lots of people. Worse things could have befallen me. And yeah, sometimes other kids (and occasionally adults) said nasty stuff about my being adopted; but kids say lots of nasty stuff to each other, whether the object of their ridicule happens to be an adopted peer or an ugly teacher or whatever. That’s childhood for you.
As far as feeling like I wasn’t really the “real” child of my adoptive parents, of course I felt that way. That’s because I’m not genetically related. I accept that. My family and I joke about it a lot. They are more like each other than I am like them, which I do attribute in this case to our genetic differences. But it certainly doesn’t make me unhappy. We are a very close family and get along about as well as anybody could want.
My adopted child status did, however, turn me into a spectacular overachiever. I always felt that I needed to show how grateful I was that my parents adopted me by doing really well at everything I took up. I did and still do want to make them proud. Show them that they really did get a good deal after all. Neurotic? Maybe. But it works for me.