How do you know when youre in love? Well, you lose your appetite and get heart palpitations. Oh wait, thats flu symptoms. Sorry.
I think that if you're really and truly in love with him, you won't have to question yourself if you are or not.
I wish you luck in finding the answer! :)
Moving to Relationships. :)

How do you know you're in love? I guess it probably changes from person to person.
As for me, I thought I was in love with some boys in high school, but then I met Katie. She was always there for me after my breakups, and when she stopped my tears by kissing me I knew right then and there that I was in love.
When I was around her I was always happy, she always knew what to say to make me feel better when I was down. She loved me, she understood I was hurt from past relationships and took ours slow, never rushing me into anything. And it didn't matter to her that we were lesbian, she didn't let that keep her from holding my hand or kissing me in public, ever.
Then, when she broke up with me, I cried longer and harder over it than over any other relationship I'd had. There's a void in my heart that will be there forever, and no matter who else I may fall in love with, they'll never fill it.
That's how I knew I was in love, and I still am, even if we've moved on with our lives and things have changed, she will always be the first person to truly steal my heart.