Will he ever regret breaking up with me? does he miss me?

my boyfriend of 5 months broke up with me a few days ago over the phone. I know he really liked me and we built up our relationship. he said that his ex-girlfriend who he'd met while he was in Australian and was with for a month but had been split up for 5 months had recently come back into his life (a week before we split up) and he said he can't ignore his feelings for her although his feelings for me are still strong. I think he made this decision because they have friends in common..it was one of his mates who brought her up and that there's loads of them going to Australian in about a week. he associates her with good things but that's not always how its going to be when they're back in this country. I'm gutted and upset and hurt. things were really good and I feel he's just made an impulsive decision and not really thought it through. do you think he will regret it once he's back here? and I feel like I'm the ones who an emotional mess. do you think he even misses me? please help me. its torture.

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