Being assertive/manipulative

I am facing this problem currently. I am very sensitive and fearsome. I don't like to hurt others and am scared to argue with anyone. I become very hurt if someone has a bad attitude towards me. This only ends up in my stress levels increasing and losing patience and self hatred. Colleagues and friends say that I am not manipulative and very straightforward and that is what causes so many problems to me. I feel that I should not care whether others are good with me or are bad with me. But I tend to become over reactive suddenly and this is creating a chain of problems. I am sure in Buddhism, there would be the way to solve my problem.