As the last two posts show, there are two ways to look at it;
1. You've only been going out a week so maybe give him a bit of a chance
2. You've only been going out a week and he's already invaded your privacy.
Both quite valid I suppose so it's up to you, but yes, he was in the wrong, and you probably aren't overreacting.
Talk to him about it perhaps, see what his attitude to it is; he might realise his mistake and whatnot and you can move on, or maybe he believes that's a reasonable way to act, and it's a trait you just hadn't noticed before that's going to be an issue for the duration of your relationship.