I can absolutely relate to your description! In fact, just yesterday I began a similar topic in General social chat (it's called How to be less boring)
I just constantly feel like I must play a role, I constantly think about what's considered normal and expected of me. I can be funny too, and I can get creative and do silly things which I enjoy. However exactly the same as you, I still think it's a mask, a role I'm playing.
I hear people constantly saying just be yourself! However for me there's no self. I don't have any deeper desires or anything that is unique to me. I'm just constantly playing roles but otherwise I have no idea who I am.
I had a difficult childhood where I had to suppress my own desires and likes /dislikes so I constantly did everything in order not to cause trouble and to fit in.
I remember how I bought a sticker album of backstreet boys, although I couldn't care less. I only did it because other girls in my class had it. This is just one example but I did and still do similar "fake" things even now as an adult. Because I'm unable to choose my own hobbies, clothing style or anything, unless I copy it from someone else or unless I have clear instructions about how to do something. At the same time I'm not really depressed, I'm usually in a normal mood with natural ups and downs, but it's not clinical depression. It's just like I simply have no idea what to do unless I can copy from someone. Or unless I have instructions for something, or I can see certain patterns which I can copy or base my role playing on.
I'm absolutely not trying to be fake or pretend, it's simply I have very little inner motivation.
Is that similar to you?
I'm very sorry I can't give you any advice, just tried to say you're not alone. I think it's either related to trauma or mild aspergers.