Ok I know being physical is unacceptable, but what you did is unforgivable.

Obviously she wasn't completely over her ex when you two first got together. You knew this damn well when you were with her. Yeah, it's tiring and it requires unimaginable patience and energy but you did exactly what you wanted to do - instead of giving her space and time to move on, you wanted to be with her through that. That was your choice.

Yes she wasn't over her ex. Yeah she probably cried and complained about her ex to you. Very frustrating. Very painful to watch your loved one hung up on somebody else. I get it. But after she finally opened up, trusted and loved you, and had to find out your shadiness on your phone,... Think about how dumb and betrayed she must've felt. At least you knew about her and her ex upfront. She found out you cheated on her a long time ago with a dude and she had no ****ing clue. You didn't even have the guts to be honest with her as soon as it happened. You cheated and took the easier way out by not saying anything to her, hoping she'd never find out. You did that only to save yourself.

& Justifying your cheating by saying "oh well she put me through a lot with her ex" ?? And lying to her about it til you knew you had no way out? That's just complete BS and that's very immature.
Own up to your mistake. Come clean. Apologize without comparing faults and who hurt whom more.

But it sounds like the damage has been done - how will you two come back from this? The trust is gone. I'm not saying it's impossible but I'm telling you right now, it's gonna require a TON of effort from both of you if you want to make this work.

Ugh this just broke my heart