I've struggled with this as well. I struggled with depression when I was in my teens, and when I tried to express it, everyone told me I had to reason to feel like I did and to get over it. I also was really shy as well, (social anxiety? I don't know.), coupled with low self esteem. I think a lot of my life I would act as others would want me to respond and ignore how I felt. A lot of my behavior was approval seeking I think. Probably due to my early childhood. My mom was always at work and my dad had a habit of taking a bunch of pills and passing out on the couch.

I tackled these problems over time. The social part, I just pushed through. I get the tension in the pit of my stomach, but I just take a deep breath and say something intelligible when I talk. The self esteem is a roller coaster somedays. When I feel depressed my self esteem usually follows. For that I remind myself of all the things I have accomplished and try to let go of the things I failed at and made mistakes. Expressing emotions is still difficult for me. Some emotions are easier than other, laughter and happiness, joy were the easier ones to express. I struggle with expressing sadness. Frustration I can, but not really anger. I get mad, but I don't tend to yell or anything. I especially have a difficult time expressing anger towards other people. I think it's been over 5 years since I raised my voice at someone. I try to focus what is making me mad, and how do I resolve it.

The more I bottle up, the more mixed emotions I feel and the harder it is to untangle what is making me feel, happy, sad, depressed, etc. My advice is to start with the easy stuff. Laughter is probably the easiest I would think. Maybe do some soul searching and try to figure out what caused you to not show emotions. You said you feel, happy, sad etc.