Worms and other intestinal parasites typically cause belly bloat and diarrhea. Impacted anal glands will cause constipation. Examine her anus. If it is red and puffy, it is probably impacted and she will need to see a vet.
Sometimes with cats it can be difficult to tell if they're licking their rectum or genitals. Could this be possible? Is she going frequently to the litter box or squatting in places other than her litter box? If so, she may have a urinary infection and should be seen by your vet. Female cats don't seem to get urinary blockages like males do, but they do, indeed, get urinary infections.
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Anal sacs and worms are the things that come to mind. Have the vet take a look. If it is tapeworms, she will need a prescription from the vet anyway (it's not something over-the-counter medicines take care of).
Has she been spayed?..if not she could be in heat.
or yes could be worms...
she could be very constipated? when has she had a bowel movement that you know of?
could also be her anal glands are impacted.
answer the above questions so we are more able to help you
my cat did that after having somthing burst. its a little vessle that they dont use if not treat it can kill them. take her to a vwt asp to be looked at. she could just nhave worms but better safe them sorry