How about I "stalk" my boyfriend before we get together soon.
Why? Is your boyfriend stalking you?
I wanted to know if he is that into me.
You shouldn't stalk others to find out their true feelings. They may feel like you're violating their boundaries. Using honesty to find out how they actually feel is one way to find out the truth while not upsetting them in the process.
You're just jealous that I have a boyfriend.
He may not be your boyfriend just yet. You shouldn't stalk others just to find things out. You want to give them their privacy if you end up together in the future.