Why do people treat me like rubbish?

Im sick of being treated like rubbish by others. It's seems like a repeating pattern throughout my life. Surely I'm not that bad of a person so why do people look down on me and treat me badly. Everyone looks down their nose at me or underestimates me. I'm always being patronised or condescened down too. I always try not to come across as a soft touch but I suppose certain people see through that facade. I have put great effort into not being seen as approachable so people wouldnt take advantage but people can sense that I'm not that confident. Just wondering it others have the same issue?