I seem to struggle showing my true emotions

Sometimes we utilize humor to mask our true feelings because at some point in life we learn that it is risky to feel vulnerable. This is very common and it's a defense you have built over time. As you have noticed yourself, this can lead to us not feeling authentic and holding those feelings inside instead of being able to express them. The anger you mention may be linked to this holding of feelings because when we are unable to express how we feel, we store it in our bodies instead.

Anger is a bit like an inflated balloon; once it reaches its limit, it explodes uncontrollably. If we are able to let it out a little at a time, it becomes more manageable, we hold less, and that limit is much less likely to be stretched. Being able to express how you feel instead of masking it with sarcasm is a skill, it takes time and practice to learn. As with learning any new skill, it is likely that you will make mistakes along the way. A good way to begin this process is just to recognize what you are feeling. You can begin to do this by setting aside a few minutes each day to just check-in with yourself and notice how you feel. Simply recognizing the feeling within yourself can be really powerful.

Feelings exist to inform you about other people, the world around you and the world within you. Ignoring how you feel does not eradicate that feeling, it just buries it until it is triggered again. Repeatedly doing this means that all these feelings get sort of mushed up together and this can get quite overwhelming so that the next time you feel something, you really don't want to deal with that because it means dealing with all of it and who wants to deal with years' worth of emotions? Taking the time to separate each emotion, recognize it and understand where it is coming from puts you back in control. Your feeling is acknowledged so it doesn't need to wait to be seen, it's done its job and can rest. 

We all have a thinking brain and a feeling brain and we need both to make decisions which are truly best for ourselves. Really paying attention to how we feel requires a willingness to feel vulnerable and this is a scary thought but did you know that thoughts are often more scary than the actual experience?