Help am I being paranoid here?

[manga42]

I will try to keep the story brief, a few weeks ago I came home from a trip (husband still away with work too) and found a letter had been posted to me, this letter told me my husband was not a nice person at work basically and that because of this they thought I should know he had been having an affair for some time with a manager at work! it was very out the blue, I waited until he came home and challenged him, which of course was met with complete denial and a very long explanation about issues at work and that as a senior member of the management team they obviously felt aggrieved and this letter was just that 'to cause trouble'. I did some research myself and in fact there is no manager of the department in question mentioned in the letter, and the only senior member in that team is a man!!
I questioned him and challenged him a lot over a few days, a lot added up and some did not of which I never fully got an answer or to the bottom of.
In short I chose to believe him and move on however I find myself now snooping and questioning what he's doing. He has gone away tonight for something to do with his hobby which he does attend every year but is going alone this year, I found him ironing favourite shirts late last night to take despite him having plenty ironed already. I'm not of proud of it but earlier this week I snooped in his brief case and he had a wad of cash £350 quid which I don't know why, this is unusual and we share an account!!
There are various small things I notice along with being over attentive that I can not put my finger on but my gut tells me something is not right!
I just don't know what to do, he is very clever at talking and quick thinking, and I'm finding myself pulling away - what's an outsiders view here guys?
Thanks

I just don't know what I should do really, as has been said, it would be horrible if innocent to discover someone was recording you or what ever I know I would feel gutted at such distrust, however in the other hand I do have reason to question things and I have not really had satisfactory answers.
He also seems causal about it and as someone else mentioned trying to just sweep it under the carpet. I know if it was the other way round id be furious at the unjust implications made to me and would be wanting to investigate
I agree with the comment that I feel a little vulnerable as I do not know what has happened whether that's an affair or something else, what I do know is that people don't generally do something like this unless they do feel aggrieved and so what has he done to push someone to feel angry enough to want to wreck his home life?!!
Some people have asked how his behaviour has been and I would say only change is at times he is suffocating me, over attentive/needy...I mentioned this to him and said I feel like I'm being punished even though the letter was accusing him not me!!
Regarding the money, I've never raised it as have not admitted I saw it, he did not come back from said trip with any purchases so I really don't know what it was spent on!
What do I do, if I snoop I could make it worse, if I do nothing and it turns out to be something I will feel pissed at myself for burying my head in the sand.
The business trip that is referred to in the card he leaves for at the weekend and I feel pretty low about it :(

Have you spoken to him about this new letter? I think you really have to, and you have to be together on this.

Have you considered involving the police?

I have re-read, i see he's casual about it.

I don't think I would be casual, its creepy at the very least. I don't like the fact he's checking your phone either.

that said.... it means he's spying on you, and without any justification. You at least have method in your madness.

Call the PI and see what you can unearth. KNowing something or nothing is better than suspecting there is something going on but not being sure. At least if there is something he's up to you will know and be in a better position to make decisions.

If he's using his car at the weekend a VAR is the way to go!