You're in the perfect position, my friend
. Next time you're in bed together, after you've eaten her pussy and made her cum (at least twice, I recommend), move on south and eat her asshole. Throughout this entire process, tell her how amazing she tastes and how good you want to make her feel. Then start fingering her asshole, moving back to lick her pussy again. Lap at her clit- or if she's too sensitive after cumming, tongue fuck her pussy- while you're fingering her ass. Then add another finger in her ass and a thumb in her pussy. Hopefully you'll be giving her clit a tongue lashing at this time, while you have two fingers and a thumb in her greasy holes. After about 5 minutes of this, maybe as much as 10, she should be in heaven.
When you feel the time is right, pull your face away from her pussy, wipe your mouth off and go up to kiss her. At this point you should start fucking her normally. Ideally, mish first, then doggie. In doggie, you should work a thumb in her asshole. You really should fuck her this way until she cums again. When she does, she should be perfectly primed for anal. You've associated all those great feelings with her ass, so she'll be game. Ask her point blank something like, "Baby, do you want to feel me in your ass now?" Looking at her straight in the eyes while saying this may help. She'll probably moan a yes, at which point you should start lubing her up, but again going to lick her pussy. Work in a couple of fingers while lubing. Try to work in three or four, if you want- very slowly and gradually, of course. She'll barely be able to stand waiting for the actual penetration if you do this right.
After she's fully lubed, get her in a position she's really comfortable in. Doggie is okay, provided that she can balance herself alright without really thinking about it. Don't just try the "ass up, head down" �naked people movies� position that you may really want to do right off the bat. That's for next time
. It's best to just throw her over a couch, with her tits resting over the highest point, her body matching the curve of the couch, being fully supported by it. When penetrating her, go extremely slowly. Getting a girth of 5 3/4" in a virgin asshole won't be easy. Just concentrate on getting the head in past the two rings of her sphincter. In fact, it's best if you have a finger in her pussy, while you have her rub her clit throughout this process. It'll keep her relaxed. You just have to pay a lot of attention to her body and encourage her to talk to you.
Once you're past her two rings, just stop dead. Ask her how it feels. Talk to her. Tell her how good you feel and how hard she's going to cum. You may have to stay still in her ass for as much as 10 minutes. You might also try taking the part of your dick outside her ass with one hand and rotating it gently, depending on how she feels and reacts. Once her sphincter has relaxed enough, go deeper. Anyway, I think you know the rest. The key to any kind of good sex is communication, both of the bodily and verbal variety. A girl won't let you anywhere near her ass if she doesn't trust you. Your girlfriend clearly does, from what you've indicated. If you can reassure her that you want to fuck her in the ass for her pleasure first and yours second, you'll definitely get a shot at the tighter passage.
Some other important points:
-your girl doesn't seem to be too concerned about the cleanliness factor; having her take a shit beforehand is an absolute must, but you may want to give her an enema as well. If you feel very comfortable talking about it before anything happens, go ahead and do it. Flush her out a few times until the water comes out clear. You'll be all set at that point.
-using a condom is another absolute must, to prevent infection first and to hold off from cumming too soon second. Later on when you perfect giving your girl enemas and not popping off too soon, you can ditch the condom. Just be careful. Get yourselves tested for STDs at least once every 6 months.
-you may only get half your cock in the first time, due to the initial tightness. Don't be discouraged. You'll get in there the next time, or the time after that. A seasoned asshole can take more cock than the pussy can. There's a thread on this board about that, if you want to check it out.
That's it. Sorry for the long, drawn-out post, but I think you have to be very thorough when discussing this topic. You have it made and you should take advantage of this terrific opportunity. Your girlfriend may very well cum harder than she ever has before and your cock will get squeezed like it never has before, if she does.
