This is a long prayer, but I'm hoping it will help you like it did me. I got it from the book the nook- The Power of Prayer to Change Your Marriage:
INFIDELITY�PROTECTION...Lord,�I�pray�You�will�protect�my�marriage�from�any�kind�of�infidelity.�May�audultry�be�far�from�us�and�NEVER�find�a�place�in�either�of�our�minds�and�hearts.�Pour�Your�wisdom�into�us�so�that�we�are�too�smart�to�allow�the�enemy�to�sneak�up�on�our�blind�side�and�throw�temptation�in�our�path.�I�pray�that�You�would�not�allow�temptation�to�even�come�near�us.�Keep�us�far�from�ANYONE�who�would�try�to�lead�us�into�something�evil.�REMOVE�anyone�from�our�lives�that�would�ever�tempt�us�with�audulterous�thoughts.�Lord,�please�give�us�the�ability�to�see�danger�in�advance�and�the�wisdom�to�not�do�anything�sinful.�Help�us�to�live�in�integrity�before�You�and�each�other�so�that�we�will�walk�securly.�Establish�us�in�our�faith.�Keep�us�from�being�deceived�by�our�enemy�and�the�world.�Thank�You,�Lord,�that�we�are�complete�in�You�and�need�not�seek�anything�outside�of�what�You�have�given�us�in�each�other�and�in�You.�In�Jesus'�name�I�pray.�Amen.

Oops... Guess there's a limit to the Amy of characters you can use here. Look for the book. It's by Stormie Omartian.

INFIDELITY�PROTECTION...Lord,�I�pray�You�will�protect�my�marriage�from�any�kind�of�infidelity.�May�audultry�be�far�from�us�and�NEVER�find�a�place�in�either�of�our�minds�and�hearts.�Pour�Your�wisdom�into�us�so�that�we�are�too�smart�to�allow�the�enemy�to�sneak�up�on�our�blind�side�and�throw�temptation�in�our�path.�I�pray�that�You�would�not�allow�temptation�to�even�come�near�us.�Keep�us�far�from�ANYONE�who�would�try�to�lead�us�into�something�evil.�REMOVE�anyone�from�our�lives�that�would�ever�tempt�us�with�audulterous�thoughts.�Lord,�please�give�us�the�ability�to�see�danger�in�advance�and�the�wisdom�to�not�do�anything�sinful.�Help�us�to�live�in�integrity�before�You�and�each�other�so�that�we�will�walk�securly.�Establish�us�in�our�faith.�Keep�us�from�being�deceived�by�our�enemy�and�the�world.�Thank�You,�Lord,�that�we�are�complete�in�You�and�need�not�seek�anything�outside�of�what�You�have�given�us�in�each�other�and�in�You.�In�Jesus'�name�I�pray.�Amen.�