If you choose not to, then you'll risk losing your boyfriend.
If you choose to do it, then you'll have two boyfriends. If it works, awesome you kept your primary bf and gained another one. If it doesn't, you'll lose your bf.
Worse case scenario between the two is the exact same, so it's much better to choose the best case scenario between the two: to try poly.
True Love is neither physical, nor romantic.
True Love is an acceptance of all that is, has been, will be and will not be.