I had returned for my follow up visit with the clinic after going with Zack for the special project that the doctors had. When I showed up the nurse told me that just Dr. Topinbottom would be performing the exam. I didn't really care, I just wanted the money that he was going to pay me for the study. It was only a moment later that Dr. Topinbottom walked into the room and was ready to get started. He did say that he would need another sample to give the lab, because yesterday just wasn't going to be enough. Taking off my shirt the Doc started by listening to my heart rate, and taking my blood pressure. After that he had me do 10 push-ups and sit-ups, so that he could take my blood pressure again. I felt like I was getting a workout at the doctor's office, and afterward he took my heart rate as well. Finding it a little elevated he asked how I felt after a workout and sexual activity. But, most of the time I never had any issues that I would complain of. Putting on a pair of gloves the doctor proceeded to take off my jean shorts. Then, feeling my stomach and pubic areas he looked for any tender areas. After he didn't find any, he pulled off my underwear so that I was naked on the exam table. The was where he examined my package and then told me that he wanted to take my temperature. To no surprise he said that he wanted to do it anally. He had me move to the end of the exam table and put my feet up in the stirrups. He lubed up the thermometer and inserted it into my asshole. Holding it there for a moment he wanted to make sure that he could get a reading. Taking it out he looked at it closely and said that I appeared to be normal. His next order of business to check off was that he needed to do more of an anal exam. To loosen me up, he started with lubing his finger up. Inserting it into my hole, right away he said that my muscles were responding normally. He had me squeeze tightly down on his finger before he head me relax. Then, Dr. Topinbottom moved his finger in and out of my ass. He made sure to get in nice and deep, as far as his finger would go. As soon as he was done, he took it out and said that it was time to take a look inside my hole. Looking inside the tool box, he pulled out this instrument that was all metal and shiny. He covered it in lube, and started to push it inside. Once inside, a part of the middle of the instrument pulled out. This was what allowed the doctor to see all the way inside my ass. However, he said that he still needed to see up further and to do that he was going to need a longer instrument. The one that he grabbed looked huge, and even though he said that it would be easy, it was a little hard to believe at the time. Pushing it slowly, my hole just swallowed the long metal tube and I couldn't help but moan to let out some of what I was feeling. Using a flashlight he looked deep inside a couple of times, until he said that he had seen enough. Then, he proceeded to take it out, and was very careful in doing that. After he was done the next thing that he had to complete was getting a sample and to do that he needed me to get hard. The Doc gave me an option, I could get hard myself or I could have his help to do it. I thought for just a second before I replied and said that I would take his help. Gripping my dick, he took a firm hold of it, and placed my cock in his mouth for him to start sucking on. Dr. Topinbottom was very good at giving head, and able to get me hard. He would twist his head from side to side, and in an up and down motion at the same time. After a while of it though, I could tell that he was getting tired and he asked me to take over and jerk off. I did so and as I got close to shooting my load, I told him and he took over jerking me off. I held back as long as I could and I shot a couple times over the cup that he had in his hand. Squeezing my dick forward I couldn't help, but setup since my dick was so sensitive. As soon as the last drop was out, the Doc said that he wanted a taste of his own medicine. I hopped off the table and helped him strip off his clothes, and he took a position on the exam table. Right away I started with giving him head, and Dr. Topinbottom would thrust his cock into my mouth. To make it as easy a I could used a combination of sucking and jerking off together to try and get him off. He wanted me to jerk him off to get him to cum. The Doc took over stroking his dick and I rubbed his balls and kept my face down by his cock. He started to moan pretty load and before I knew it he shot a load on my face. Covering my neck down to my chin with his cum, most of it still ended up getting all over him. On my way out the Doc told me that he wanted me to schedule an appointment to come back in next week for some more experiments. That was great because at this rate I might bet this months tuition paid off early.