Will plan b work??

I'm 2.5 months postpartum, my bday was yesterday so my bf and I had a few drinks last night after we put the kids to bed and my sister stayed over to help with the baby so we probably had a little more than we should have. I'm not on birth control right now but we've been using condoms every single time. I was pretty drunk so I went to lay down and at some point during the night we ended up having sex after my bf came to bed I thought he used a condom because I always tell him to but turns out he didn't and he didn't tell me🤦‍♀️🤦‍♀️ when I got up this morning to use the bathroom there was cum on my underwear now I'm panicking. I shouldn't have drank as much as I did and I regret it now. My cycle isn't back to regular yet so idk when or if I've even ovulated or when my period is due, will a plan b work? Or is there a chance I could end up pregnant? I've never taken one before so not sure how they work but I'm terrified I'm gonna be pregnant now