“But how can you love two people at once?”

I get that one a lot, too. My preferred response is that I find love is not a finite resource.

I’m not sure if you were present in the workshop I said this in at BiCon, but I find it incredibly easy to love multiple people: I am so close to some of my friends I would happily tell them I loved them* but not in “that way”.
At the same time, there may be someone or even some people that I’m in love with. (Though I often find it hard to differentiate between the two, or when one becomes the other.)

* if I didn’t dislike the phrase so much; as Snow Patrol put it so well, “I don’t quite know how to say how I feel. Those three words are said too much; they’re not enough.”