Should I break up with my boyfriend?

You wrote:
"He has opened up to me about the fact he is polyamorous"
Right then and there, he needs to go for two reasons:
1. Anyone who uses the phrase "polyamorous" is weak-minded, naïve, or immature.
No one in the real world except psychiatrists and psychologists ever said "polyamorous" until about 7 years ago. This is just liberal bullshit (and I am a liberal saying this!) percolating into the population - a technical term that should have remained technical among those in that field, not something that should be cavalierly asserted by those not with the mental discipline to use it.
The people who do use it are easily susceptible to fads or whatever the lastest craze or wacky science asserts. It's echo authorities as if you are the authority as well and, sadly, all to often, the "authorities" aren't very disciplined and authoritative.
2. He's immature and needs to grow up. He doesn't love you. A man in real love is not "polyamorous" no matter what his dick says because the brain of a man in love overrides anything his dick says otherwise. Trust me - I know what I am talking about on this one.
Bottom Line:
He needs to go.
ASAP.
You're not only incompatible but risk getting a std if you have unprotected sex with him
Opinion
4Opinion
If it's not meant to be, it's not meant to be. Why put yourself through something, you're not comfortable with, if you're not happy
Yes, of course you should.
Welcome to being out of the honeymoon phase
Ya think?
Leave him
Superb Opinion