Yes, but I ignored those feelings, chalked it up to a bad day, and stayed in the relationship. Ditto the next time I had those feelings. And the next. And the next. Finally I realized I was kidding myself and wasting her time, so I broke it off. It was the right decision. I only wish I'd done it sooner and saved us both a lot of heartache.
But that's me. I'm not telling you to go dump the guy. I'm telling you not to ignore those feelings. Fleeting moments of doubt can pop up in most relationships, but if they persist, your heart is telling you something, and you should listen. If you keep having to ask yourself if you're in love, you probably aren't.
Love should be powerful, thrilling, all-consuming at first, then secure, confident, and forged strong by time and experience as it grows. Nowhere along the way should you settle for "I guess I'm in love."
On the other hand, maybe you're just having a bad day. But I doubt it.