boyfriend and his ex

My boyfriend and I have been together for a year and a half and his ex and her boyfriend have been together for around a year. Weird situation, so his ex is one of my close friends and I'm kinda worried that my boyfriend still has feelings for her. He hates her boyfriend for no reason, he reckons that she still looks at him like she's in love with him when that's the way I see him look at her. I don't know what to do😓