I have been diagnosed with moderate rectocele. is there anything i can do to prevent it from worsening without resorting to a pessary ring?

Kegel's might help: A rectocele is a vaginal type of hernia. So, there is a damage to the tissues. Kegel's pelvic floor exercises may keep it from worsening, but it won't improve on its own. Pessaries "push" the hernia back mechanically. Surgery can also be a possibility.

Vaginal bulge: Rectoceles can cause difficulty completing bowel movements, sometimes uncomfortable sex. One way to help prevent worsening is to treat constipation and avoid straining with bowel movements. Consult a gyn or urogynecologist if you have not.