Virginia is a no fault and also a fault state for grounds. Here you need to hire a private investigator to obtain the evidence that is admissible in court
(1) On the application of either party if and when the husband and wife have lived separate and apart without any cohabitation and without interruption for one year. In any case where the parties have entered into a separation agreement and there are no minor children either born of the parties, born of either party and adopted by the other or adopted by both parties, a divorce may be decreed on application if and when the husband and wife have lived separately and apart without cohabitation and without interruption for six months.
(1) For adultery; or for sodomy or buggery committed outside the marriage; (2) Where either of the parties subsequent to the marriage has been convicted of a felony, sentenced to confinement for more than one year and confined for such felony subsequent to such conviction, and cohabitation has not been resumed after knowledge of such confinement (in which case no pardon granted to the party so sentenced shall restore such party to his or her conjugal rights); (3) Where either party has been guilty of cruelty, caused reasonable apprehension of bodily hurt, or willfully deserted or abandoned the other, such divorce may be decreed to the innocent party after a period of one year from the date of such act. (Virginia Code - Title 20 - Sections: 20-91)
Since it is a long term marriage you will be entitled to alimony
The court, in determining whether to award support and maintenance for a spouse, shall consider the circumstances and factors which contributed to the dissolution of the marriage, specifically including adultery and any other ground for divorce under the provisions of subdivision (3) or (6) of § 20-91 or § 20-95.
You will also be entitled to at least half of his pension and the marital property including the house. Virginia is an "equitable distribution" state, the marital property shall be divided in an equitable fashion. Equitable does not mean equal, but rather what is fair. The court will encourage the parties to reach a settlement on property and debt issues otherwise the court will declare the property award.
Here you need to make an appointment with a good local divorce attorney.