Hi. i was wondering if you could possibly tell me what could be causing me to have pain in what feels like my deep vaginal muscles after running ?

Weak pelvic support.: Without doing an internal exam, my answer is theoretical. The muscles that support the bladder and uterus constitute the "pelvic floor." With pelvic floor weakness, the bladder and uterus may descend and cause a sensation of fullness in the vaginal area. Usually there are other symptoms, like urinary stress incontinence. It's uncommon in young women who've never been pregnant.