WTH Anus Pressure??

So, this is my 3rd pregnancy but Ive never felt this type of pain at 29 weeks. I went to sleep, and was snoring away when I started feeling pressure from where my butthole is. Mind you Im still sleep!!! But starting to wake up from it. So I finally wake up in disbelief because it felt like a "hard poop" but I knew I didnt have to poo. I waited 15 mins for it to go away completely. Can anyone ANYONE tell me what this might have been?? I had no braxton hicks in my tummy, just my butt and tailbone. 😂