Unsure what to do exactly?

Ultimately, do what makes you happy. Just know that there is always the possibility that you and this other guy won't work out. And that your current boyfriend will have no obligation to take you back, if you end up wanting that at any point in time (if the other relationship doesn't work out). Of course you deserve your shot at happiness, like everyone else, but just be prepared to accept the possible consequences that may come of it.

The best way to find out what he wants is to talk to him about it. If you guys are close friends you should be able to have a honest conversation with him and ask him about how he feels and any questions you may have. Just take your time making a decision after you hear what he says. A 3 year relationship is a lot to throw away so just make sure you have a clear mind about what you want.

If you'd dump your current SO for this other guy if you knew he was interested, then you probably should dump your current SO anyway. Maybe I'm weird, but I just don't get the point of being with someone if you KNOW for a fact that you'd prefer someone else. It seems to me that would mean that person is not the right person for you.

I guy you should try to test how possesive he is for you in specific. Try checking out other guys and lets know how he feels. Or a big staredown at him if makes him uncomfortable than he migth be intrested in you. The best way to it in a very silent and romantic place with utmost of privacy m sure at that point he will reveal his true feelings fo sure if he got any. Thats the best shot you have according to me.