I know you want to be first in his life, but you’ve chosen someone who is making it clear to you you’re not as important to him as you’d like to be. Since you’ve only invested five months in this relationship you’re lucky because it won’t be as hard to cut bait and swim as it would if you’d been involved for years.
Decide what’s more important to you, being with him in fourth place or being first and foremost in a man’s life — but that man is not him. He’s someone who’s still out there and who is available for a committed monogamous relationship with you.
No one can have everything in life, so figure out what’s important to you and go for it.
I hope that helps. Let me know how it goes, and please follow me @AskAprilcom on Twitter.