A few minutes passed and Sandra walked in, she asked me to get up on the bed. I thought she was a bit cold towards me thinking maybe I misread her before but I thought I would find out. I was wearing a summer dress, hold up stockings and nothing else, I wanted to look sexy for her. I removed my dress completely and lay down on the bed naked. Sandra turned to face me and I could see her eyes widen but she said nothing and continued to place the gel on my stomach. As she placed the sensor on me she asked if I had drunk the 2 litres of water she told me to do, as she needed good pictures. I told her that I had and that I was busting more now than the last time. As Sandra was probing me, I noticed she was glancing at my crouch every now and then. I think she noticed I had shaved my pussy lips since my last visit and that they were all ready swollen waiting to be touched. As before I raised my legs up to try and take the pressure off but with twice as much fluid, it was becoming hard.
Sandra seemed to finish quickly this time and I was ready to start the fun when she told me to lie on my front with my bum raised, as she needed to do a rectal ultra sound. I asked her if this was normal and she told me it was easier to see the back of the baby from behind. (I found out afterwards she made up the story to get me to turn over) As I lay my head on the pillow I raised my ass and spread my legs, the pressure was relieved a little, as the baby was now hanging down and not squashing my bladder. Sandra went around behind me and slowly started to rub lube on my asshole. I could feel the heat of her touch as she lightly probed my ass with her finger. I felt a small squirt of pee escape my pussy and drop onto the bed but Sandra didn't react. Then I felt the sensor slowly entering my asshole. As my ass swallowed it, I started to pant and moan at the sensation as Sandra pushed it in and twisted it around.
Then all of a sudden I felt this vibration in my ass then I realised that it was no sensor but a vibrator. As Sandra was pulling it in and out of my ass, I moaned to her I was going to piss myself. She told me to hold it in a little longer. (I think she gets off on the desperation part). I held onto it a little longer as she reamed my ass with the vibrator but the time had come for release. I slid my hand under me and spread my lips and grunted as I let go. The force of my pee jetted out spraying Sandra in the chest as it ran down the front of her lab coat. Then she leaned forward and placed her mouth over my leaking cunt and started to drink all of my piss. As she was drinking, I started to rub my clit wanting to cum in her mouth just like last time. There was so much piss that she couldn't take all of it as it poured out of her mouth and pooled around my knees on the bed.
I was in heaven my big hard nipples brushing on the bed sheet as my piss subsided and I was about to cum in Sandra's mouth yet again, when all of a sudden Sandra stood up and told me to lie down on my back. I was so close to cumming that I pleaded with her to finish me off. She growled at me and I remember her saying " do as you are fucking told and get on your back". I was scared now I'd never seen this side of her before. I thought about getting out when, I looked up and saw her standing behind me on a small stool, she had unbuttoned her soaked lab coat (she was stark naked underneath) reached down and pulled her pussy lips wide and started spray warm piss all over me. (She had removed her cloths outside after the office girl had left unbeknowence to me)