Is it possible to not like yourself and do people take advantage of this?

I am 20 and in college and somewhere last year, I lost sight of who I am. I lost sight of everyithng that I stood for and believed. I changed who I was to appease people around me and to be accepted. I think people close to me saw this insecurity and pounced on it. Heard the saying people feed on weakness and i kind of think thats true now. How could I expect others to like me and respect me when I dont like or respect myself? I feel that is where my life began to go downhill: When I began to shape who I was in order to please everyone else. Can anyone relate and give me advice to be my own person?