For example, none of my friends have seen me mad or sad or excited. I really haven't felt any of these emotions for years, and it's hard to communicate to people at times when I don't understand what to say or do in certain situations. I always get confused when this happens, and don't know what to do.
I've always tried to make people feel better about themselves, or make them happy, caring more about them than me. I almost never give my opinion because I'm afraid what people think of me. If someone asks me a question about my opinion, I'd just say it's fine or something along those lines.
Anyway, is there something I can do to get these emotions back somehow?
Hopefully that all made sense. Sorry for the long post.
Talking about your feelings inside may be a good way to start, it will help you understand how you actually feel inside, and showing emotions MAY get a tad bit easier.
Also feeling uncomfortable around people may cause you to hide your emotions, giving opinions can't be wrong, they are opinions for a reason and it's always good to express what you think, instead of bottling everything up inside.
I recommend talking about how you feel to someone, in private, it will help you understand what your emotions are about certain things and it might help you to start expressing your feelings. However, you are not alone, there are other people out there like you.
Feel free to message me if you want to talk.
I am actually very similar to this, and i have depression... i'm too scared of failure to even try to succeed and my opinions change every time somebody opposes what i say.
This is almost exactly what I mean.