First I'm so sorry for your sitation but you are in great "hands" here at MB.
It will be difficult to readily trust your spouse once trust has been broken but as many here have said.. it takes time.. I know time seems to be against us BS but unfortunately the only way thru it is thru "IT"
You can request things in the meantime from your WS such as transparency in the relatinship (ie. open access to email accounts, passwords, cell phone, bank statements etc.) or whatever it waas that helped him aid in his deception.
My FWS had two email affairs and also was secret with his cell phone. Now that we are hopefully in recovery, I have the passwords of his email accounts, changed his cell phone number and I have his password to that. Also, I have requested his cell phone be on ring at all times and in the bedroom during the night. I have full control over all money. He calls me when he arrives to work, IM's me throughout the entire day, calls me on his way home.. and we just started MC.
And yet I'm still insecure and dont' trust him.. but that's b/c it all takes time.. Eventually if things continue as they are, then that will be earned back. IF you snoop and do not find anything.. then I would interpret that as a good thing. and just trust in the saying "everything done in the dark will come to the light" Eventually. In the meantime if you wish your marriage to work.. forgive, and try to move on. Talk to him and express what your feeling, It would help if he is patient and understanding throughout this time.
Would you be willing to provide more details on the A?, Each situation is unique to every one of us but we have some great "experts" here willing to help
Take Care