Is my landlord allowed to go in my room without permission?

I just got home after a long holiday and I found the windows unlocked and slightly ajar. As I never open one of those windows, I knew someone had been in my room, and since nothing was missing or out of place I highly suspect my landlord. He did not give any indication that he would be going into my room. He did call me when I was on holiday but didn't leave a voice message. When I called back, he said "The painters needed something but it's been taken care of." There were people painting the back of the building that week, but I was given no notice that I would have to leave the windows open or that someone could go in my room. Is there anything legally I should do? There are private belongings in my room that I feel very uncomfortable with my landlord potentially seeing and I have no idea whether he only opened the windows or, for example, went through my stuff. I feel unsafe knowing he came into my room while I was away and I don't know what to do now or what actions I could take.