Orgasmic Exercise

I have a question that I hope im able to find an answer to on here. At the gym one of the ab exercises I do is a hanging leg lift where I hold onto a bar and then raise my knees to my chest. An odd thing happens when I do it though after a few reps this tingling in my lower abdominal region begins to build that is pleasurable and intense almost to the point of a little frightening. I’m wondering what is going on down there to cause this and if I continue doing reps the sensation gets even more intense. I’ve never had a true orgasm I believe and I think this is something linked to it. If anyone has any clue what’s happening please enlighten me.