Trust me...you're not. In fact, you are going to have to realize that in the real world, at some point, the BFF will start to fade away as you and the boyfriend get more serious. You'll get to the point where you all hang out on occasion but nothing of frequency.
It's just how things work. It's nobody's fault, its just how things work. Even if your BFF was a chick, you would do the same thing and then you'd both call each other and talk about how you never hang out, only to never hang out or have to make some plan way in advance.
You should however have a talk with the BFF so that there are no hard feelings. While there shouldn't be, what should be and what happens don't always coincide.
Make sure you do stay in communication and what not because when things go awry that's who you're going to call and who you're going to need.
Also, how does the boyfriend feel about the BFF. That could play into as well.