Her tears and 'shame' were/are not for you. That was her reaction to being caught and loosing her lover. She hesitated to say she loved you because she didn't want to give up the OM.
BTW: a deep kiss is really a big deal. In our culture it's an intimate act/boundary reserved for someone that you have strong feelings for. In addition, studies show that the 'kiss' was the last barrier/boundary/restraint that once crossed leads to sex.
The kiss is evidence that she had lost control of the relationship or concern for you - and headed for sex.
The roller coaster of emotions (love, hate, anger, disgust, depression) you feel are typical when cheated on.
You need to take at least 90 days (extend as necessary) to give yourself time to stabilize so you can make a decision you're comfortable with.
See your doctor asap. Your doctor can help with sleep loss and the roller coaster of emotions.
Inform her that your immediate reaction is to break up with her - but you will postpone a final decision for 90 days so you can calm down.
Inform her that because of her behavior she is no longer trustworthy (her words, excuses,promises mean nothing).
In the 90 day interim she should prove to you through her actions that she may deserve a second chance.
1 - Postpone the wedding for at least a year.
2 - No sex. Human beings are hotwired to have sex in these circumstances. It's called hysterical bonding. Don't do it. It confuses your long term rational thought process.
3- Move to another bedroom.
4 - Act like a roommate - not a life partner. Distance yourself physically and emotionally. Be civil but stop being her intimate friend, fixing her car, giving her emotional support, ...
5- If distancing yourself pushes her away, then you already lost her. She should be pursuing you, taking the initiative and doing back flips to prove she deserves another chance.
[This message edited by Robert22205https at 6:28 AM, June 4th (Friday)]