gut instinct or being paranoid? need help!

My best friend has a bit of a reputation of getting around men, has been with all of my OH friends and even cousins! Can never keep a relationship for longer than a month. She's been my best friend all my life and I love her to pieces but when I first met my OH she was there and she wanted him and in her words "if nobody is having him I'll be having him by the end of tonight" we ended up together and we moved in together, my best friend had nowhere to live so we took her in, her and OH got on really well and everything was great until he kept suggesting she slept in our room while her bed was being delivered at the bottom of our, saying she's got the body of Lilly Allen which he found quite hot, saying we should all lie in bed and Watch films. I didn't think much of it until recently they've been acting strange in front of each other, barely talking or when we are in the living area she doesn't come in anymore or when he gets home from work she goes to her bed and tonight he went straight into our room after work until she went to bed. On Saturday night I got spiked in the club, had to be put to bed because I was pretty much unconscious and he text her to borrow her charger yet our 3 chargers were in the living area! His excuse was he was too drunk to see them. I have a habit of over thinking and literally nobody else to speak to. What do you guys think?