I understand you love your wife. But love is a two way street. Looks like your wife had an affair much before your marriage. The best solution is to go for counselling. Convice your in-laws to make their daughter understand. Go to a professional for a marriage counselling. The affair she has with her boyfriend is illegal. And you can seek divorce on this basis. But you love your wife. Suppose she agrees for counselling there are two possibilities:
1. She still wants to be with her boyfriend. Then you must divorce her and seek a new beginning.
2. She understands that she has hurt you and decides to leave her boyfriend and have a new start in your marriage.
I hope its the second case. But to be more practical, dont expect any physical relationship as yet. Its not possible. Let her get attached to you emotionally first. And how long would this extra marital affair last? what you have with you wife is legal. You are her husband and no one can change that. But if she has been forced to marry you, her parents are at fault. They have ruined three lives.
Please do go for a marriage counselling. I wish you all the best!