Thanks everyone for your replies - we did talk about this and the BF is getting better with it - the first day he was really mad but now he's not exactly happy but he isn't spitting mad anymore. he does understand why I read it - trust is a big issue for me and I have a hard time trusting anyone - he didnt take it too personally. We actually did talk about some things in the journal that bothered me so I do feel better about him/us.
I do wonder though for someone who finds this so important why he does casually leave it around in places where I coudl find it. He does bring it to my house to write in it before bed on the days he sleeps over, and sometimes forgets it there - however, you'd think he'd guard it with his life if he was that concerned about his privacy.. anyhow.. thats a mystery that i am not sure i will solve.
We do have a good network of support - individual and couples T so we are not left hanging with these issues unresolved. In fact we were discussing marriage last year but we put it off for a year to deal with issues.
Thanks everyone... I feel a bit better but still not great. I am still upset at what I did, as well I am really scared now as I just have to trust him words instead of finding out "for sure" what he thinks in his journal. I highly doubt that I'll get away with reading it again without some serious repercussions so its definitely something I wont do again.