Although Catherine and Susan are now studying to be medical specialists, when I met them they were in their final year as medical students. A friend of mine at college had advised me to try to have 3 girlfriends at any one time. The rationale was that female students don't want a "needy" boyfriend -- they want an independent boyfriend who is available intermittently. With that in mind I had negotiated my way through many girlfriends when I met Catherine and Susan at a campus function. By trial and error I had worked out what is successful and what isn't.
After a week or so I had been successful in bedding both Catherine and Susan. I had to put up with their insecurities and their desire for me to wear condoms. The first rule in the first few weeks is to give them a good time and to give them orgasms. I was confident that my rewards would follow with time.
After a few weeks I casually mentioned to Catherine one night that I was having regular sex with Susan and that Susan didn't get me to use condoms. Catherine was on the pill and so she agreed to let me fuck her without condoms. I started enjoying just cumming in her cunt. The next time I was with Susan I mentioned the opposite -- that Catherine didn't get me to wear condoms and again Susan agreed that I could cum inside her.
Although they were friends they never seemed to discuss what was happening sexually with me -- I think it is just a girl-thing. They both loved dirty stories and they especially loved hearing about what the other was doing when she fucked -- but all the information flowed through me. Occasionally I'd have a third girlfriend as well, but Catherine and Susan became my main source of sex for quite a while. They thought it was cool that I didn't ring them frequently like previous boyfriends and let them study.
Over many months we worked through sucking my cock, swallowing my cum, doggy style, sucking me after I'd fucked their pussy, fucking up against the wall -- all on the basis that the other one was already doing it. So, for example, when I suggested to Catherine that we park the car at the look-out and fuck, I told her that Susan had already done it with me -- Catherine then agreed and I could then truthfully report the details of our car-fuck to Susan who would then agree to do the same.
On average I was probably fucking each of them every 10 days and our fucking was becoming more and more exotic. So combined with an occasional third girlfriend I was probably getting sex 7 or 8 times a month. I even got them to agree to fuck during their periods.
During this time they graduated and both became interns in the main city hospital. I was a bit concerned about what their change in status would mean -- but the cycle of fucking continued uninterrupted. As long as I was the conduit of information, each of them continued to keep up with the other. It never ceased to amaze me that during this time, although they saw each other frequently, none of this sexual activity was discussed.