Very Confused Person. To get out of it.

From the last few years i am facing issue of shyness, not able to speek properly in front of people, not able to speak up for the right things. This made me a person like eveeybody is using me, not valuing my efforts they only look for their benefits. Peoples uses this emotion of mine and used to push or press the voice of mine. They feel i am a very confused person and we will surpress the feeling and put pressure on me. People always uses my ability, helping nature for their benefit and then turn around. I am always a kind hearted person, always ready to help someone who in need, but in my case when i help peoples they use me. I feel like why peoples are doing this to me. Always me. Why peoples are not able to understand me. I feel i am having a attitude problem. I feel that peoples do not accept me as their friend. Only freind in benefit feeling. I lost many freinds in the past few years. Not talking to my classmates too. please suggest me a way to get out of it.