If you truly live her try to commit on another level. Attractivness will always fade its the chatacter that does not. Most women only cheat to exit the relationship. Most men will cheat to feel the 'high' as you've said and checking you've still 'got it'.

With the questions you are asking her it sounds like there is doubt in your mind of if she loves you. Women are used to been the ones cared for and tended to and compliments etc whereas men are expected to shake it off and crack on which is shitty because men have feelings too. Maybe this is where it has stemmed from? It sounds like you are seeking validation from her.

Obviously you cant divert the blame to her as this is fully your fault but clearly some underlying issues are there that you need to sort out. You need to discuss openly with your partner and commuincate better.

Reading peoples cheating stories really helps you understand why you might have done it and the ripple effect of it. I would recommend reading some and seeing if any of the sitations are similar to yours.