I make out with my best friend

So my best friend and I (both girls) became friends a little over a year ago. We clicked instantly, practically inseparable. We cuddled all the time, more than the average friendship I think but we never thought about it. That developed into giving eachother back massages and cuddling for hours then a couple weeks ago we just started kissing. We made out a few times, we talked about it openly. We love eachother so much, but not in a romantic way, we both consider ourselves straight but are open to the possibility of dating although we both don't think that's the answer. We still kiss all the time and sometimes it even gets pretty heated but we don't see it ever going farther than this. We just can't stop making out and don't understand why. Help???