Express feelings

My man friend says I have an issue with expressing my true feelings. I don't talk about ill feelings that I have because I don't like the pressure of feeling exposed, being rejected, or being taken advantage of. Everytime I want to talk to him about how I feel I never do it or I don't say everything I need to. Just a little bit then I just discuss other things. Not my emotions tho. It's to the point that I don't even know how to feel because there are so many bottled emotions. How do you express your feelings without worrying so much about the outcome ?