A lot of guys enjoy anal stimulation because of their prostate. For girls, or at least for me, it's a lot different. I tried it for the first time a couple of weeks ago, and he could only go in halfway before I made him stop. It literally felt like I had the urge to poop or I was pooping backwards. He used lube and a condom and went really slow. It turns me on when I think about it, but when I do it, it sucks. So what's the problem? Do I have to keep doing it to enjoy it? Will I never enjoy it? Any advice is appreciated, from girls or guys!
You're right that during anal sex quite a bit of pleasure does come from the prostate being stimulated, but the majority of the pleasurable sensation simply comes from the nerves around and just inside the anus, so it's not like only people with prostates will enjoy receptive anal sex. That feeling where you need to poo is caused by pressure on some sensitive nerves in the rectum. The nerves are triggered by crap after it moved into the rectum and this is what tells you that you need to go - however they will also be triggered by a penis or fingers or anything else that goes up there. After a little while you will desensitise to that urge and it won't be a problem - this is a psychological thing as the nerves will still be firing, you've just got to 'train' your brain to ignore them when you are having sex. It's just a matter of practice.
As a guy, I find anal sex very pleasing. I don't know if it's because of the prostate or something else. I share your urge to poop, at least at the beginning and I think that contributes a little to the pleasure. The only difference I reckon between a man's and a woman's rectum and anus is the prostate, so I'm guessing it must be it. Also, did you feel at least a little bit of pleasure? Because if you did, the problem could be not relaxing enough and not using enough lube. But if you didn't feel even a little. It may not be pleasurable even with careful approach. You could try for example massaging the anus itself, or making your boyfriend try sticking just the tip. Since, if I remember well, only the anus and a short part after it have nerves with pleasurable spots. Hope this helps. Ask me anything if you're still unsure.(*hug*)
I know quite a few women who love anal sex - it just takes time and practice. A couple of the women I know say they enjoy anal sex because it rubs against the G-spot from a different direction, and the pressure feels good against the vaginal walls. You just have to be patient - especially because the idea turns you on.