Devastated over his affair.?

I found out August 2009 my husband was having an affair. He said the affair lasted 3mon, but he met the other woman August 2008. I always had my doubts about the time frame of his affair. I believed he took a trip to Bahamas with the other woman August 2008, I asked him about this trip and he denied it. I asked him so many times throughout the last year and a half and he continued to deny it. I found out today he did in fact go to the Bahamas with the other woman. I’m devastated! We were trying to work through the affair, (he ended the affair once i found out) but this just reopened a very hurtful, painful wound. I’m numb and at a loss of words. I asked him, told him I have the proof and he continues to say he didn’t go with her and why am I mad about something that happened that long ago, Which to me also prove that you did go on this vacation. Please I need your advise Would you be upset about this? Should I just let it go?