I was walking along the lake shore with my girlfriend once when she said she needed to have a really big shit. She said she'd been holding it a few days and she really had to go. I told her it was a bad idea to hold your poo for too long as it can cause health problems. She said there weren't any toilets out here so she'd hold it untill we got back but I insisted she went in the woods. She refused to do that and tried to hold it in spite of her desperation. Half an hour later she stopped walking and said she couldn't hold it any longer and moved her legs apart. A wet patch formed in her jeans as she pissed herself and then I smelled her poo. The back of her jeans swelled out as she loaded her knickers with a lot of poo and the bulge grew at the front as well where she'd held it so long. The look of relief on her face was a picture but it must have been very embarrassing for her. I needed to poo as well so to make her feel better I started to go in my pants and wet myself too. She gave me a big hug for that and when we got back we had the most amazing sex.