THOU SHALL NOT COMMIT ADULTERY.Why is this a commandment from God?How come Christians even Pastors?

often lose the battle,when it comes down to obeying this law..First befour you judge me to harshly,I did not expect this,or wish for this,and feel as though I have no control at all with the thoughts that are in my head,,and as a christian woman that thought at one time I was indeed saved by the blood of christ,now I wonder ,because I'am not as strong as what some might be if given the chance to do what I would like to do.I'am very confused as to why God allowed me to get in a situation as to where these thoughts were able to come about,knowing how vulnerable my marriage is.Any insight to these questions will be most appreciated.Here is my story, my husband of 11 years has made love to me only twice in a year 1/2,because of a lack of desire between the both of us, we still love each other,and want to grow old with each other.Recently me and my pastor were doing a church thing absent of all the other church members,and ever since then in short every time I see my pastor,I WANT HIM HELP