Is that normal poop in my pants ???!!!

I date my bf for more than 3 years, everything were O.K until from small period we tried to make anal , it made a lot of pain for me and cried alot but he enjoyed my hole so much
then he asked to make that again but I was afraid and refused but he told me that I would enjoy anal after I used to it after little times
I was patient till it becomes so easy to make it in and out like my pussy
after that problems start im my life
1st I found very small pieces of shit im my pants without feeling how it comes!!!!
2nd I need to go to toilet to poo after any fat dishes and can not hold it
finally and the miserable thing at last time we were making anal I shiiting and everything were brown even her penis and I was so depressed
Is that normal and how can I avoid that ??!!