Is it normal to want an open relationship

I think it's normal you want that. I am in a very happy open relationship for quite a while already.

It can work so great, if both partners are capable of separating feelings and sex from one another.

Still, your boyfriend does not sound interested in that, it may be in both of your interests to move on. It's no use to cause either you or him too much pain in this process that will end up frustrating either or both of you in the long run.

End this and make clear what you are looking for right from the beginning next time! If you are slightly bi-interested, you can use that as an extra "bargain" element, many guys seem to dream of threesomes with their girlfriend and another girl. But be aware of what you get into...it's one thing to know the partner openly lives their sexuality with other people when you are not there...it's something else to see him in another girl while you are present, that can be a turn-on or a huge jealousy spike...find out before getting into this situation what's more likely for you.