The tissue might be your bladder or it could be your uterus.
Pelvic organ prolapse is a general term to describe a few conditions where a pelvic organ protrudes (or "caves in") to the vagina. The uterus can sag forward from its normal place in the back of the vagina toward the front; the bladder can cave into the vagina from above, and so forth.
Your uterus is normally held in place inside your pelvis with various muscles, tissue, and ligaments. Sometimes because of childbirth the muscles weaken. Also, as a woman ages and with a natural loss of estrogen, the uterus can collapse into the vaginal canal, causing a prolapsed uterus.
A cystocele is herniation of the upper front vaginal wall where a part of the bladder bulges into the vagina.
Enterocele is the herniation of the upper rear vaginal wall where a portion of the intestines bulges into the vagina.
Rectocele is the herniation of the lower rear vaginal wall where the rectum bulges into the vagina.
I recommend that you be examined by a gynecologist because you may need a pessary. A pessary is a device that is inserted inside the vagina to hold the other organs up in their usual places out of the vagina.
Or you may require surgery to replace the organs.