Nauseous Feeling. IDK why?

So this guy on tumblr starts following me and I followed him back (both of our blogs are nsfw so that's how we bonded). We start talking to one another, and we interact with each other practically daily on the site. We start flirting with one another via messenger and replies and there's this attraction between the both of us because we've mentioned it. Idk why but after talking to him for about 3 weeks I start feeling queasy just thinking about him.

I'm not sure if it's in a bad way because I enjoy talking to him. Even though we're both aware of our attractions we can have a decent convo and it's never weird. Just writing about this I'm nauseous. He's a cool dude, very pleasant, and easy to talk to. We've never met in person because we live on 2 different continents, but it's not that big of a deal. I don't know why I'm acting so weird? I'm able to be myself when I talk to him and like I said I really enjoy talking to him. It's just that lately I've been feeling like there's a pit in my stomach and I don't know why. This feeling hasn't really happened to me before.

I would talk to my friends, but they don't know I'm talking to this guy let alone running a sex blog. I don't want to feel weird about it with them so I've come to you all.