Help!

Okay so. I did something bad. I violated my boyfriend's trust and looked at his phone. Long story.. Been together 6 months and met online. He went on holiday and came back a different person and I just knew something was up. I've only ever had the urge to check someone's phone once before and lo and behold he was cheating on me. So I had this urge again, a sixth sense, an intuition. And there it was... A message to his ex (he was engaged to her, together 5 years but he had a year long affair so they split up) it was the longest, most romantically beautifully written message I've ever read. Saying how he wanted her back (been broke up over a year now) and that he wanted her to be there on holiday with him and lots more romantic things. I could barely get a "wish you were here babe" from him. This was obviously a kick in the gut, I love him very much and he is amazing,he told me he loved me and we have already had some amazing experiences together. The ex fobbed him off and nothing else has been said and he's still acting like everything is fine with me and organising dates etc? Am I plan b? I did something bad but found out something worse.. Advice please.

What do you think you should do? What are your options? Do you feel like plan B? Would you be ok with being "plan B"?

I wondered what other people would do in this situation? He's cheated before in his past. and it doesn't look like he's changed. I just don't think he should he dating whilst he has these type of feelings. I would love to be his plan a but only when the time is right?

I don't understand the question in your last post. Maybe because English is not my native language. Please elaborate. What are you going to do?