Kol hakavod on your increased observance!
Guilt is a very powerful force, and when channeled in a positive framework it can motivate us to change and improve ourselves. The process of teshuvah allows us to transform our guilt and sins and redefine and recreate ourselves. If however, we dwell on our guilty feelings and allow them to fester within us without motivating us to change, then guilt becomes destructive. Instead of focusing on your guilty feelings, we urge you to change your focus to positive, constructive actions and thoughts.
Going forward, you do not have to disclose your background to a date until your relationship becomes serious. Further, as long as your chatan knows that you are not a virgin, he may accept a ketubah with the language and financial terms of a virgin. Therefore you do not need to change the language of the ketubah.
Please note that a woman who has had relations with someone whom she is not permitted to marry (such as a non-Jew or a close relative) is not permitted to marry a kohen.
We encourage you to develop a relationship with a rabbi/rabbi's wife or mentor who can further guide you on path of observance.
We wish you much hatzlacha!