It could be her just expressing her anal glands, but I would take her to the vet to make sure that it isn't something more serious, like constipation, from eating something she shouldn't have. Call your local vet and give them a description - hopefully they'll be able to give you some advice.
If she starts acting less like herself, or stops eating/drinking, bring her to the vet right away, because she could be getting sicker.
Hopefully it isn't serious and she'll be alright :)
sounds serious yes. need to get her to the vet.
if i were you i would get a new boyfriend or keep him away from your cat. no seriously,if it lasts 4 more than a daAY I WOULD TAKE HER 2 THE VET. BUT THATS BECAUSE I HAVE NO IDEA what it could b.