My girlfriend claims I am the first guy she has ever enjoyed anal with. I don't quite believe her, and I am wondering if you can tell whether a girl has had a lot of anal sex by looking at her. I've read that a woman with anal experience has an asshole that looks like a fully-opened rose instead of a rose bud. I like our sex life a lot but I don't want to be a sucker.
I am having a hard time imagining just how much anal sex you would have to have to permanently alter the shape or structure of the anus. The "anal profile," to coin a phrase, varies quite a bit from one woman to another. This is a matter of nature, not sexual experience. Though it could be that your girl is lucky enough to be built so that she more easily enjoys anal sex, compared to a woman with a more narrow aperture.
Has something else happened in this relationship to make you believe that she is trying to deceive you? Have you caught her being untruthful about nonsexual things, like her job, her family, her finances, or the rest of her life story? Or are you coming out of a bad situation in which you know lies were told to you? Seems to be that the core problem in this relationship is not her experience (or lack of it) but your lack of trust. What would it take to create or rebuild enough trust in this relationship that you could relax and feel like it's safe to accept her at her word? Until you are clear about this, you won't be able to tell a good relationship from a questionable one.
I wish I could say that the only orifice you should consult if you want to know somebody's sexual history is their mouth. But I know better than to claim that people don't lie about what they've been up to pleasure-wise before they landed with their current lover. Have you done or said anything to this woman that would make her feel that it wasn't safe for her to be candid? Sadly, many of us have a double standard. We feel just fine about our own level of sexual experience, but if we find out that a partner has slept with more people than we have or done things with them that we don't know about or don't like, a frosty tone can creep into the conversation—not to mention the lovemaking. We are living in a pretty judgmental culture, after all, and so it's hard to feel blessed or lucky that we have gotten the attention of someone who's done a lot of living and still finds us attractive. A sexwise bed partner could be seen as much more of an asset than anything else if we weren't so prone to feeling insecure about ourselves.
Sadly, this dynamic is even more exaggerated in male/female relations. The man is supposed to be the sexual initiator and the adventurer. What gives a man sexual prowess and knowledge can make a woman seem tarnished or tainted. Unless you work hard to counteract this attitude in yourself and in your communication with your lover, she might wisely decide to hold a few things back just to keep the relationship running more smoothly.
I don't know for a fact what is going on in your relationship. But I did want to throw a few different possibilities out there so you could take inventory and decide what you want your next move to be. My advice is to hold off on taking anything to the next level until you are sure you can let your guard down with her. But at the same time, take a look at your own values or prejudices, and make sure you aren't creating a situation in which it isn't safe to be honest. In the meantime, enjoy the sex—that part of the relationship is working well, at least.