What Causes Severe Vaginal Pain And Constipation?

Hi, for the past few months i have been experiencing severe shooting pains at the top of my vagina everytime i try and go to the toilet. I'm constipated and pushing is so horrifically painful i struggle. I'm getting worried because i thought it would go however it hasn't. It isn't getting any worse but is still painful. I am 20 years old, have IBS however feel this is unrelated and weight 10st