Butterfly/pulsating feeling in lower rectum?

Hi all, Apologies in advance if this is TMI but I feel at a loss.. I am a 30 year old female, no kids, never had any unusual feelings or problems with bowels other than tingling in legs when I left the urge to pass stools but that never bothered me & I felt it was normal. A few days ago I passed a particularly hard stool, I strained as I was in a rush at the time (I know.. bad idea!) but after I wiped & stood up I felt the most unusual feeling just on the inside of my butt hole.. it felt like a little bubble or a pop of something, I describe it like perhaps a butterfly flapping when I move in certain positions. It happens after I pass gas also. It keeps coming and going & shocks me every time. I went to the doctor, he couldn’t see any Hemorrhoids as that was the first option to rule out so he sent me to A&E at the hospital and ordered a sigmoidoscope. The doctors weren’t available and I have to wait a few weeks. In the meantime one general doctor stuck here finger up there & felt around a little bit. She didn’t seem to think she could feel much & I was sent home. But this random sensation is still happening & i’m not sure what it could be. There’s no pain, just this sudden shocking bubbling/fluttering/popping twang every now & then. Does anyone have any ideas? I’m quite worried & I have quite bad anxiety passing stools. Any help would be wonderful. Many thanks

sounds like a muscle spasm maybe. i get this occasionally