need some woman advise/opinion

Renata
Hi ladies,
Ok, this is what's been going on, I'll start from the beginning.... and like to hear some HONEST opinions of women....
Somehwere in June I had a realy bad dream about my wife cheating. It was almost real and scared the hell out of me, also because I never dream (or at least, don't remember them). So I told my wife about it and she told me everything is ok and there is nothing to worry about.
Later that month she went to a concert  together with our daughters. At that concert they also met some friends of us with their children. Those friends where there with their new neighbour who was there with his son, so he and my wife were introduced to each other.
I met that guy later that month, when we just had a beer together with those friends who were also on the concert. Still nothing special going on....
Somewhere in the beginning of July I got this strange feeling and did something that I am still ashamed of: went through my wife's mobile phone. I noticed an sms where she wrote her best friend that Roman (the guy's name) also was about to join for a beer, but he couldn't because he had work to do. But that she was totally ok with it and it's better not to see him....
That's where my alarm bells started to rinkle...
A day before our holiday, my wife went running (she always does this about 3x a week already for a long tome). She stayed away longer than usual and I was getting worried, because it was dakr and also the children were afraid that something happened to mummy. So, I went out with the children to go and look for her. I found her at our friends house outside talking (where Roman is building his house next to) to our friebds and saw Roman standing next to her as well. When I came he went back to work. I got angry, because it was real late, we were together with our friends earlier that night and also we had plenty of things to do, since we were leaving on holiday the next day. We got a bit into a fight (only verbal of course). Apparently she looked on the internet for Roman's phone number because lter that night she texted him. 
To get things clear, I don't believe in friendship between women and man. Most of the time it goes wrong at one of the two and feelings come up. In the wordt case both get feelings.....
During our holiday I recieved our phone bill in my email (got through the company and automaticaly get a specified bill) and for the first time ever i went through the details. 
Of course I noticed his number several times and confronted her with it. She told me that it's only a normal conversation and have nothing to worry about. Also she got angry that I went through the bill. I asked her if she could please stop writing with him and she sad ok. Via via I found out that she was still writing with him during the holiday. Of course all messages on the phone were deleted.
When we got back she bought a new phone number and said that she didn't like that I was looking at the bill. This made my alarm bells going mad! 
Then 25th of August I was at home and my wife was outside, when I heard a sound. Didn't recognised the sound so started looking, founding out that it was her new phone ringing and recognised the number. Shit, she promised me on the way back from holiday that she would not contact him anymore, he means nothing to her so it's jo problem for her. So how could he know her new number???
I confronted her again and she admitted that the last time they wrote was on the 9th of August (day after she bought the new phonw). I checked it and this was right (at least when it comes to mobile phones).....
This was on the 1st of September and she promised me that this realy was the last time and that I have nothing to worry about. She destroyed the sim card of the new phone and told me that I am the only one for her, it was just about friendship.
 When I recieved the bill of Spetember I decided to look again and noticed that the 1st of September they spoke over the phone for about 15minutes (btw, right after she telling me that everything is ok and jave nothing to worry about). 
She swore to me that nothing ever happened between them....
Now I would like to ask: am I paranoid and is there really nothing to worry about? I believe that nothing happened (because I was on top of it from the start), but am not sure if there weren't any feelings from her side. Why else would she all do this??
I think we are happy, we have no problems, are financially healthy, have great sex, and have plenty of love between us, but this whole situation makes me nervous...
Thank you for your honest woman opinion!