He snuck into my apartment

So me and my current boyfriend have been together for about 9 months, so it’s nothing super knew. He’s been over quite a lot, and so he knows where i keep my spare key in the hallway of my lofts floor. Although last night I’m almost positive he was here without me knowing?? When I woke up, his jacket was on my bedroom floor and I’m 100% positive it wasn’t there before. There is no doubt in my mind it wasn’t there before bc it would have been the only thing on my floor so I would have noticed. The weird part is, when I confronted him and just casually asked if he’d been over, he said no. I said I found his jacket on my floor, and he said he must have left it there another night, which is hella false bc he had it on last Tuesday and he didn’t come over. It doesn’t add up, and I’m honestly hella creeped out. Why was he in my room??? Why didn’t he wake me up?? Why is he lying about it? Has he done this before?? I HAVE SO MANY QUESTIONS, but how do I approach asking him more without him getting defensive and thinking I’m attacking him?