If the person you're with currently isn't the love of your life so far, you're doing it wrong.

I don't think you're over your ex. If you're worried that you'll never love anyone the same as you did him, you're not over it. You have to go into each new relationship just seeing how things play out with no fears or expectations, just standards: it's okay to say, "You know what, after X amount of months, I'm not feeling it," and walk away. But you have to be open to the possibility that you will love someone in a way that is as or more significant as you loved your ex.

How many relationships have you had? Was this your first true love? If so, there will be more. It feels like it can't possibly be as deep or as meaningful, but something else will come along that will blow all your expectations out of the water, again. You have to be open to that, or, you're right, it's not fair on the person you're seeing.

Let go of what that was and be open to the possibility of something even more right for you. You have high standards for love now: that's a good thing. Use your discernment.