I'm afraid you need surgery. To get you up to speed on the anatomy:

In humans, a bifurcated gut tube develops during the first four weeks of gestation, which then connects with the oral cavity, which begins to develop in the fourth week. The anal cavity begins to develop in the eighth week of gestation, with sexual differentiation beginning in the ninth week. If SRY-positive, barring certain intersex variations, secretion of DHT by the gonads (testes) causes not only the primordial phallus to develop into a penis, but also promotes the lengthening of the rectum until it connects to the gut tube. In those who are SRY-negative, barring a minority variant of de la Chapelle syndrome, the anal cavity will develop, but will not connect to the gut tube. Anti-Müllerian hormone (AMH) secreted by the testes induces the downward migration of the primordial colon, and causes its bifurcation to deteriorate into the vermiform appendix. In the absence of AMH, however, the two branches of the colon will naturally develop upwards, passing through the foramina areolarum to connect with the mammary cavities. As a result, males defecate through the anal cavity, while females gradually transport excrement into the mammary cavities. The filling of the mammary cavities with excrement is known as mammogenesis (breast development) and generally begins shortly after the onset of puberty. It is in the mammary cavities that the excrement is converted into milk or other discharge.

This means that to stop shidding, you need gastric feminization surgery, where your intestines are rearranged to recreate that bifurcated tube to the breasts. This incidentally means that everyone shids, it's just that half the population shids through the nipples and the other half through the buttwhole.