Is it weird that my Bestie and Bf/ex Bf get along so well?

My Bf recently Ex but hopeful that we will get back together.. Gets along with my best friend so well. she looks just like me and acts just like me, we both have very simular personalities. sometimes i think they get along to well and laugh all the time,so loud and i feel left out! and it frustrates me.

They are both Extremley Loyal people. He is so very against cheating and is very honest, sometimes too honest. and she is the type of friend that would never jeopodize our friendship. so i feel very bad for thinking this.. but its something that is natural to me to think that. Also cause i know he thinks she is very attractive and wanted to have a 3some with her and me, because my ex and i had a 3some with her a year before. But its so different cause im IN LOVE with Him.. and i dont want it to happen.. we all agreed it would be weird if we all were to do it and dont want to anymore!

he says to me he thinks she is a cool chick and she listens to him, he said its just also good to have an outside opinion, coz were in a relatinship, there is my opinion and then the outside opinion.. he would sit me down and explain this to me cause he could see i was worried..

He was very serious to me, he got Tattoos, and constantly told me he wanted a future with me... Am i silly for tinking this or is it natural?