I need advice

I really have no one to talk to about this kind of stuff so I guess i'll just write about it here.
So I'm in a relationship with someone that I love very much. She always makes my day brighter with everything she does, she's amazing. I've never felt so connected to anyone before her. She's my world and it really hurts me to know that I'm hiding such a big part of my life from her.

It's something that will always be a huge part of me and I won't be able to hide itt for much longer and I hope that she will understand when I tell her. I'm just really scared of her reaction.

I don't know what to do.