HelloKitty, welcome and well met!
I very much understand what you are going through. From reading how you describe your situation, it seems you might actually be gay, or so close that it makes no difference. This obviously makes things with long-term bf a bit hard. Have you discussed this option? There are mixed-orientation relationships out there but they are hard work.
I am not sure if all the three of you moving in together at this point would be a good thing or only aggravate the situation further.
Me: bi female in my twenties