how do you know if you really love someone?

I always thought that love was just something you knew. It just comes to you. For instance, with my last boyfriend (ugh), I figured it out when, out of the blue (I was washing dishes at work, for christ's sake), I just thought "I love him." I'd think that if you still have thoughts like that, it could very well be love.

But judging from your question, you probably dont have those random moments very much. Like others have said, mix it up a little bit. Take a vacation, with or without your partner, and see how it feels. I do have to agree with Sass that if you're asking yourself these questions, it may not be love. But mix things up a bit before making a decision... sometimes boredom in a set routine can lead to that 'fire' going out.

Jam it back in, in the dark.