Should I tell someone my feelings (e.g having a strong attraction to the same gender) if I’m not quite sure of my sexuality yet?

It's perfectly okay to tell someone, "I think I might be _________" even if you're not sure. If I were in your position, I'd probably only tell someone I'm incredibly close to so I could have someone to work through my confusion with, but I'd say do whatever you're comfortable with. Even if you decide to publicly come out and later figured out that your sexuality is something else, that's perfectly okay! There's no rule against it!

Yeah, there is nothing wrong about that. You should tell them that you are still questioning but you think you might be that sexuality. This way, they can understand you or even help you find your sexuality. You do not have to be 100% sure. Just by telling them that you are not sure yet will be okay. So I'd say go for it, even if they do not like it it is who you are and you cannot change that because you do not have any control over it. Tell them if you want to, it does not matter if you are still questioning.