One of these days you'll both realize that your sexual past is just part of your past, and isn't a big deal, regardless of how experienced or in-experienced you are.

She shouldn't be ashamed of her sexual past, and you shouldn't be threatened by her sexual past.

You also shouldn't be ashamed or insecure about your lack of a sexual past either.

I, for one, am glad that my wife had a sexual past before me. It allowed her to figure out what she liked and didn't like, and while we've learned a lot about what works for us over the past 15 years of marriage, it was great coming into it with a base level of experience and understanding both of our own bodies, desires and preferences.

Good luck to you both, I hope you can get past your insecurities so you can get back to enjoying each others company.