
calling your relationship itself haram is a self report. if that is his move, sin is sin regardless of whether it's continuous or repeated. honestly i hope you're part of the few exceptions but this sort of behavior is common among men who have no real intention of marrying outside their religion unless you intend to convert.
again, either sin or don't sin. there's no difference between a sin that's temporary if there's intent to continue sinning and one without breaks. it's nonsense and hypocritical to use the qur'an only when it's convenient. interfaith with muslim men is halal with conditions like s5.v5 and s2.v221 which includes trinitarian catholics. wishing the best, just cautioning with a common situation that often has an unfavorable outcome.