Cat is very clingy, arches its back, low voice — in heat again or sick?

Your description matches a female cat in heat, which usually lasts 7-10 days and recurs every 2-3 weeks if not bred. Without pregnancy, intervals shorten or heat becomes continuous, with clinginess, rolling, howling, raised rear and swollen vulva.

Heat raises sensitivity to males and risk of escaping. Keep doors and windows closed. Some cats lose appetite and thin out; severe cases get pyometra or mammary disease.

If you don’t plan to breed her, spay at a vet after heat ends, which stops the behavior.