Nakakalungkot yung ganito... Yung walang proper healing and rebuilding of marriage na naganap after the first infidelity. Parang stage 1 cancer na naglead na to stage 4.
How did you address ba the first infidelity?
Did she demand that you answer her many questions regarding your affairs?
Did she demand any behavioral requests from you for her to feel safe (eg report your whereabouts, go home directly after office)?
Did she express anger and outrage because of the trauma caused by infidelity?
Did she understand why you have cheated in the first place?
These should come from her since she's the one injured. Kung walang ganyang kaganapan, that means she took it all silently. And the things happening now in your relationship are just manifestations of buried anger and unhealed wounds. Infidelity is a traumatic event. Due to it's interpersonal nature, mas grabe yan sa trauma inflicted by calamities. Hindi mo pa alam, baka may mga previous traumas pa yan in her earlier life.
However, if she did all these, and you did your best to respond to her demands/requests, and she's presently cheating on you, then the problem is with her.
Bumaligtad na mundo niyo ngayon. Sya na straying spouse, and you're the faithful one. Kung hiwalay yung sagot sa resulting problem niyo ngayon, I'm sure maraming advices na mabibigay.
Kung sakaling magbalikan kayo, you still need professional help. You need info on how to rebuild a broken marriage and heal old wounds. Without these info, cycle cycle lang. Parang nangyayari sa inyo ngayon, dahil no proper healing and rebuilding took place.
Like what others have said, for the love of yourself, tell her na you will leave her if she will not cut the ties from the other man. Give a date. Actually nga, baka ganun din yung ginawa nya sayo due to your affairs. Sabi mo kasi sexual relationships, so more than one. She couldn't leave physically, that's why she left emotionally, long before she met the guy. But to physically leave, she needs a knight in shining armor to sweep her away. I'm just assuming, I don't know the whole story.
Pero right now, na ikaw si faithful at sya si wayward, at ginagawa mo na lahat, nasayo yung bola, wala sa kanya. Actually be ready to leave her. And if she decided to really come back, seek professional help or attend retrovaille marriage seminar. Kasi from what happened in the first infidelity, you can't do it on your own without the necessary knowledge and skills to heal and rebuild. Kahit magbalikan kayo, maraming tatrabahuhin, kaya both of you have to be 100% sure and determined that this is what you want.
Kailangan nya bumalik and open her heart for forgiveness, pero kung wala ito at ayaw nya na rin talaga... Wala ka na rin magagawa. Rest in the thought that you did your best.