Could I be pregnant?

Hi guys! So about a week ago, I went to visit one of my best friends at her college and we ended up going to her boyfriends. He was drinking and she joined in, and soon he was shaming me for choosing not to and put a cup in front of me. I took a few sips but know I didn't have more than half the cup (if even half). Even though I know I didn't drink much, I don't remember a lot from that night. I do remember going into the room where my friend and I were sleeping but don't remember going to bed. As soon as we woke up, her boyfriend was pushing us to leave like ASAP, which was kinda weird to me. Then we left and I changed my clothes when we got back to her place. When I undressed, I saw that my underwear were on backwards... now, I have NEVER in my life put my underwear on backwards. I know that wasn't me. But I don't remember anything happening...