By taking it to the next level do you mean marriage and your afraid to tell her on your wedding night you've been with someone before? OR, do you mean your taking it to another level and going to have sex with her? Either way, don't wreck yourself over this. If she loves you she'll love you even if your not a virgin. But in some ways, you are, because it's going to be new to both of you right?
My best advice is be honest if it's bothering you and then relax. If she leaves you because of this then it's best to know now then when something even bigger comes along. And it will, trust me, no relationship is perfect. Good luck to you and give yourself some slack and relax.
. . A woman is like a tea bag. You never know how strong she is until she's in hot water. Eleanor Roosevelt