If your relationship breaks up because you are not sexually compatible (and only because of that), then I’m not sure it was a good relationship for you to be in anyway. Presumably she is with you because she likes you, not just because you are a great lover. If it’s all about sex, then enjoy it as long as it lasts. I hope it’s about more than sex.
Sexual skill is something you can learn. It can be fun to learn. You don’t have to worry about what someone has tried or not. You don’t have to try anything outside of what makes you both feel good. Unless you are videotaping it and putting it on the internet. But that’s a whole ‘nother story.
If you are feeling sexual insecurity, it might be that you are feeling insecurity for another reason, but just using sexual experience as a stand in. If your relationship is going to last, you gotta take the bull by the horns and talk about these things. You need to find out how important sex is to her, and what she expects from you. You also need to find out what she thinks about you in terms of the overall relationship.
Sex is about expressing feelings, in my opinion. Some people treat it like a sport, but I don’t buy that. That’s what you should worry about: are you communicating well, whether by words, feelings, or love-making. Make love, not sex. If you are communicating well, it will go a long ways towards dealing with your insecurities about the relationship.