How do I help people to be comfortable with my ways?

I am something of an introvert, but when the need arise, I can be just as sociable as any average person. I find that my co-workers are not comfortable with me or just don't like me. I used to partake in some of the conversations and I am never rude or mean to anyone. I've never denied my help when needed, not that they ever ask. I take my jobs seriously and it comes before co-workers. I do not participate in any activities, partly because it's all I can do to get through a workday with the pain I experience, amoung others. I suffered numerous serious back injuries and currently live with pain. They are constantly undermining anything I do to help me perform my duties and has sabatoge some of my work. My supervisor did not believe me when she was told. This has caused me to withdrawl more on a social level, but I continue to maintain a professional attitude and behavoir.