You're ok, OP! It's normal to want to share and also normal to not want to share! Everyone is different! Some people are more "stoic", introverted, quiet, etc. and there's nothing wrong with that or you!
I think you should talk to your partner about how they feel about the fact that you don't share much. Because we are all different, they may want you to open up a bit more or they may be indifferent towards it. Relationships are going to be a bit of a compromise.
But again, there is absolutely nothing wrong with being that way. :)
Edit: A lot of people have boring as fuck days too without much to share lol. If something interesting or funny happened during your day, your SO might appreciate a share!