Cause of lower pelvic pain with stretching pulling sensation?

Ligaments. In men and women this can be the presentation of an inguinal hernia. Other possibilities are ligaments stretching, irritation of the illioinguinal or genitofermoral nerves, or loosening of scar tissue from previous inguinal or low abdominal surgery. Pelvic mass is also possible. This is obviously a nonspecific sign so physical examination is key in helping to determine the cause. See your gp.
Many things. For women- could be a number of things: ovarian cysts, pulled groin muscles, inguinal hernias, fibroid rumors of the uterus.