Trust issues

Ok so me and my bf have been together for 2 years and we are really close, we work in the same company and I love him to bits, he has his friends and I have mine - recently one of his friends (a girl) has been messaging him loads! And she has just broken up with her boyfriend, I trust my BF with my life but I am constantly worried she is gonna try and come between us and take him away now she is single as they messaged a lot when she was in a relationship 🥺

I’ve spoken to my friends about it and they said I am right for having my concerns but agree that he loves me loads ... I need people’s help to tell me if I’m right for being concerned or if I’m over reacting and should just trust that he loves me 🤦🏼‍♀️

I’ve spoken to him about this before and expressed my concerns and he said that he isn’t into her in that way, I believe him but I have had 3 relationships break because someone came between us....

I’m scared to keep bringing it up again because I don’t want to sound possessive I’m just terrified of losing my best friend, please help because it’s making me seriously depressed 🥺🥺