Tell me its okay.

Hey all, its ridiculously late and I can't sleep, too much on my mind.
This is the first time i've felt this depressed in a long time.
I have another account on this site but in the past my girlfriend
used to read what I posted on it which kinda sucks lol.
so I'm just using this one for this post.
Well, in the past (say a month ago? not that long) I had a friend, lets call him bob. (haaaa, so original I know). So like after a while my friendship with so called 'bob' faded, which was a sad thing as it was pretty good, but I got over it soon enough. btw, bob lives very far away, it was all online this friendship. anyway, a few days later, this 'bob' is still talking to my girlfriend who made friends with him after I introduced them. I guess this is fine.
Another few days pass and I am to find out they are emailing / txting each other every day, am I wrong to find this hurtful? anyway I try my best to act cool with the matter and I guess it goes smoothly, but I do talk to my girlfriend about it. she says its nothing to worry about, ect ect, blabla all that stuff you know. so I take that into consideration. Then, a while after im told by her that he is calling me insultive words, ect. even this annoyed her. you see I met bob with a bunch of other people online, and he had upset all of them an hurt them all, except my girlfriend. she still thought he was an angel. so we all agree (me, girlfriend, and other friends who knew bob) to ignore this guy(stop contact) becasue we all agreed it was best. now I go away for a holiday a little while after this has all been a bit calmer for a while and I get told by my girlfriend on the phone (while im still on a break) that shes started talking to him again, becasue she felt bad. this was a promise she broke, as we all promised to cease contact. after I finally get over this, I get home an everythings fine, girlfriend says she stoped talkin to him. Anyway 1-2 weeks later im at home, and ( I know its wrong) I signed into her email account and I saw emails from back a month or so ago. (I know this is wrong and I cant forgive myself,) and they didnt say much, just they hurt. you can imagine what they said, its not like they were flirtin really bad but it was really friendly, (more than a normal friend) and saying hey txt me to 2nite, ect and saying yay I got more credit an then gf saying oo so u can txt me now? an bob sayin yeah if u txt me back.
It just hurt. Now I love my girlfriend more than anything in the world.
I dont know what to do.
so I go and make friendship with bob for one last time...
I felt that if she likes him that much, as hurtful as it is to accept, then we should be friends. but... I still feel hurting. I dont know if I should do or say anything, as my girlfriend hardly talks to him now anyway. But I feel just empty and ... I just need some advice I guess.
One moment I think its all fine, cuz I dont wana lose her, then the second I just feel depressed and think should I let her go ect.
been together like 4 years. she says she loves me, and shes not evil as made out. we are madly in love. I know she didnt mean to hurt me, I just dont think she knew she was. thing is shall I just leave it? its all in the past anyway. just emails brought back the hurt.
thanks for reading ~

Edited to say: I guess it just makes me feel better getting it out. Thanks ~