Your boyfriend has made his stance perfectly clear.
He is ok with you having casual sex with others, but not an emotional or romantic relationships. You have to decide whether you would be ok living the rest of your life that way.
40 yo straight female
Married in the eyes of the government to Butch since 2001...
Murf my monogamous second husband has been with me since May of 2012.
In a V relationship with an average 60/40 split of time. Only due to Murf's and Butch's crappy work schedules.