I used to be a versatile top but, a few years ago, started my transition to what I am now--a total bottom. I had no idea how or why that happened because I always enjoyed being a top because it was less work (no messy anal clean-up), and I could always find a ready bottom when I needed to get off. I am a scientific sort of guy so I thought I'd do a little research to see if there is any scientific reason that could occur. I read many articles about this phenomenon but the one that resonates with me was one that stated that there are certain chemicals/proteins present in the ejaculate that, once absorbed, create a dependency on the host's ejaculate. If I understand the article correctly, it means that a when a bottom absorbs the top's cum it changes the bottom to desire it more and more with each load. I'm not sure about how "science" would explain this, but I know that, at least anecdotally, this is true in my case. As I said earlier, I used to be a versatile top, but I was sort of tricked, over time, into bottoming. At first, I started out telling the top that he would need to always wear a condom when he topped me but, little did I know, he was stealthing me. After absorbing several of his loads this way (again, unbeknownst to me) I wanted to try bareback but with the stipulation that he not shoot his load in me. He agreed but (I found out much later) whenever he topped me, he shot his first load in me and kept fucking me until he was ready to shoot his second load. At that point he would pull out and shoot that load on my back. I absorbed several loads through this deception which continued to change me. So, after a few months of that, I realized that I wanted him to cum inside me. I told him the next time he was fucking me that I wanted him to cum in me so I could feel what that was like. He happily agreed. He shot his load in me which I pushed out once he pulled out. He didn't say anything about me doing that but after a few more weeks/sessions of him shooting in me and then me pushing it out he told me that he thought that was rude and didn't want me to do that anymore. I thought about it and decided that I would keep his loads inside of me. I have found that now I actually want his cum inside of me. It has made me into his own personal cum whore, which we both seem to enjoy.