Boyfriend telling best friend he loves her.

So, firstly me and my bf have been together for over a year and a half now, and have known each other for three. he has this best friend he's known for four or five years now, she's a female. And, a prior time before this i saw her tell him she loves him. I asked him about it, and he didn't say much, just that he "sees her as family" but, has claimed he has slept with her before. He didn't say it back, only cause I said something I think. So, anyways. Tonight I saw a message pop up on my bfs phone to his best friend saying "love you too, bruh" when, he knows how I felt about her saying it to him. And he was sitting there smiling the whole time he was texting her. I just feel really insecure about their relationship, I know I shouldn't, but I do. I just need advice, am I overracting? Side note; I'm also 31 weeks pregnant so, I could just be over emotional lol.