I've been in a relationship for about a month now and I'm incredibly happy and content with being monogamous with this person. I have a huge emotional bond (I've known her for about a year before I started having romantic feelings for her) and I have a really affectionate bond with her.

However, some acquaintances have brought up how my best friend (also of the opposite gender) and I act around each other. We've known one another since we were in middle school, and have almost as close to a platonic bond as you can really have with someone. We have absolutely zero problem doing things that would be taboo even for people in romantic relationships. We talk about our genitals to one another without even a second thought, and we have contact that most would consider sexual completely casually; we've slapped each other's asses as congratulations, she points out any noticeable erection I might get, I've grabbed her breasts to complement them, etc. We also make ironic sexual comments about anal sex, "daddy", etc. This obviously sounds weird and like this is the person I'm actually dating, but I swear this is completely casual and not weird at all for either of us. Neither of us have EVER actually had feelings for one another.

Usually I don't do the physical stuff with my friend around my girlfriend because obviously if I'm with her I'm focusing it on her. They don't have a dislike or anything either; they're actually fairly good friends since I introduced them. I guess I'm just confused; is what I'm doing...wrong? Should we really be acting this confident this casually or should we drop it so I can focus on my actual relationship?