I wouldn't say you are a creep, because I believe your intentions are innocent, but I would say you are verging on borderline stalking behaviour with the waiting in the car park. If she doesn't bring it up, don't bring it up. If she does, I don't know what you should do.

I know it would really freak me out if I found out that someone was waiting in the car park to catch a glimpse of me, even if I believed they had no intention of hurting me.

Maybe you could write a letter or email telling her how you feel and discuss in therapy? If you're not doing so great, would you consider moving your sessions closer together?