I can’t stop sniffing my friend’s **

I am in a long term, happy, sexually active relationship, which mostly is fine. Recently though, a friend of me and my girlfriend came and stayed at our house for a few days. Unbeknownst to my GF, this friend left some clothes in the room she stayed in, including a pair of dirty **. As a teenager, sniffing ** was a major fetish for me but not one I’ve had for a while. Out of curiosity though, when my GF was out of the house, I gave these ** a sniff, and the smell of her ** was intoxicating. I genuinely spent half an hour on my knees, nose buried in the ** of those ** soaking in the smell, and I’m hooked. Now any time my gf is out of the house, I’m doing nothing but sitting in the spare room sniffing our friend’s underwear. I’ve started waking up early for work so I get extra panty sniffing time before my gf wakes up in the morning. I dream about the smell. I genuinely haven’t been able to get off without thinking of it since this started just over a week ago. This friend is coming to stay again today, and I’m so worried both that she’s going to take her ** away without leaving another pair, but I also don’t know how I’m going to be able to look her in the face. All I’ll be thinking of is how much I want to bury my face between her legs and just sit there for hours. I’ve never even been especially attracted to this girl (she’s pretty, but I’m very happy in my relationship and have never been interested in anything outside of it until now) but I genuinely think I’d throw away my 3 year relationship if she told me that I could just come and take her dirty ** once a week, and that’s crazy to me. But her ** is just too delicious smelling to pass up.