I just took a look at the photos you've posted and aside from my being circumcised, our cocks are very, very, similar in shape and size, so this might help.
First, I never even start to have intercourse without a lot of foreplay. Getting your partner to ache for your cock instead of worrying about aching from it helps alot. One thing that drives my current partner crazy, is when I rub my cockhead back and forth between her vagina and clitoris until she can't take it anymore--by that time she's both psychologically receptive to a good fucking, as well as literally frothing from arousal.
Second, when you first enter her, do it very gradually, letting her savor the sensation of becoming more and more filled with you moving deeper into her body. Don't ever just try and ram it inside. If you do that, she'll both tighten up physically as well as be fixated on the idea that this is going to be all about your pleasure and wind up causing her pain. Sort of a self-fulfilling prophesy.
Third, let her tent. Almost all women "tent" after they're FULLY aroused. Whern this happens, the rcesses of their vaginas expand, sometimes greatly, but usually enough to allow much, much, deeper penetration without getting to the point of pain. Yes, when your dick is past 8", like yours and mine are, no amount of tenting will help with some girls, but I've been amazed at how much cock a woman's body can handle when you take the time and care to help her accomodate your member--even in the "doggy" position.
Fourth, watch out for her cervix. Doggy style can create some extreme variations in how your bodies line up, due to differences in leg lengths and how wide she spreads her kness apart on the bed. Done right, you'll slide up behind her cervix into the little cul-de-sac which makes up the end of her vaginal canal--done poorly and you'll score a direct hit on her cervix, at which point she'll jump and tell you "I can't do it this way, let me get on top." Guarantted. Of course talk is great for making sure that you don't poke her cervix head on. As you work your way into her, ask her "how does this feel?" And yes, LISTEN to what she says. Most likely it will lead to you feeling your balls rubbing up against her clit.
Last, until you and her are ABSOLUTELY SURE that she can take your entire length all the way inside of her in that position, don't even think of pounding away like a madman. That means fucking for a few minutes with full strokes (pubic bone fully extended towards hers) at a slow, measured, pace first. And if she's loving it, you then can let loose. My experience is that when you approach it like this, and she can take it that way, it becomes a favorite position for both partners.
Hope that helps.