Thats a hard one to decide Ray, especially if you dont know for sure exactly how the other person feels. If you knew for sure that they too felt the connection and that you both wanted to pursue a relationship together then you would be able to weigh up whether you would be happy enough that it was worth risking hurting someone. although you dont want to be hurting other people you really have to do whats best for you, what would truly make you happy? The most important thing is that you make a decision that will make you happy.
If your only concern is that you might hurt your partner, then I suggest for you to just go with the other person. What if's are the biggest regret you might have in the future. And frankly, it doesn't seem like you truly love your partner anyway, if you even consider this thought. A wise actor once said “if you love two people at the same time, choose the second. Because if you really loved the first one, you wouldn't have fallen for the second.”I hope that helped. :)
You're not worried about anything but hurting them. So, I think you should just go with the other person. You're obviously not happy with the first person since you're developing feelings with another. No shame, I've had that happen. But, you're only stringing them along if you keep this up.
"“if you love two people at the same time, choose the second. Because if you really loved the first one, you wouldn't have fallen for the second.” -Johnny DeppAlthough you don't love them. At least I don't think you do.