Am I being oversensitive or is he playing games with me?

I've been dating a sweet charming British guy for over a month I met online, but this past week he's suddenly been rather mysterious.

We had 3 amazing dates with lots of chemistry, including a dinner party he hosted for his close friends & work people that he invited me to as his date. (I did sleep with him on the 2nd date as it felt so comfortable. My other Brit friends told me in the UK, many relationships are started after a drunken shag so it's no big deal if you hook up too soon and he kept pursuing me after we had sex.)

Then I went home for 2 weeks for XMas after our 3rd date, and he would call or text to say hi every few days, wished me a merry xmas etc. Very sweet. The day after I returned he invited me over and cooked dinner for me and we cuddled. That night he talked about places he wanted to take me for future dates and things seemed perfect and genuine. He had to leave at 5am the next morning for work as usual, and just mumbled "see you later" when he left. I didn't hear a peep the rest of the day which was unusual. 3 more days of silence go by so I sent him a short text about an article I thought he'd like, not questioning him on where had he been or why I hadn't heard from him. He politely repied 8 hrs later with one text but still no mention of meeting up or asking me how my first week of work was going at my new job. I didn't respond to him until the next day as I felt hurt, but I kept my response brief, neutral and pleasant when I did and he replied right away but still no asking to see me.

That same night (4 days since I saw him), HE called twice but didn't leave a voicemail. I called him back 20 min later and his phone went straight to VM, so I left a message saying 'returning your call, wanted to see what's up.' 24 hrs later and still nothing. I haven't reached out since I left that one VM.

My over analytical mind is coming up with every scenario possible: Was he trying to dump me but chickened out? Maybe things were moving too fast and he freaked out overnight because he's not ready? Did he want to chat but his phone died/was busy with work? (the French massacre happened on Tues and it's a big deal with his news agency. He's got terrible long work hours and runs a huge department.)
I do know an old ex gf is back in town this week to get her cat he was sitting for. He told me he lost interest in her a long time ago and there's nothing there, but not sure if she's staying with him.

His dating history is a little troubling. He said he moves really slowly when committing to someone, is ok being on his own, and gets bored in relationships easily, which I definitely took note but didn't say anything. At 32, he hasn't had any serious long-term relationships and the last girl he dated was a year ago, so it doesn't seem like a priority to him as he just moved to the US. (I never ever hinted about possibly being his gf or us being together or any future talk as it's too soon, just fyi. I'm not needy or clingy with communication either.)

Thoughts?? I've never met a guy who made me feel that way, I can't explain it but I definitely think we both had something. I'm not 100% sure what's up with him now, why he would call twice and not leave a message but never call me back after days of ignoring me. It's just odd. I've been dating in NYC for a decade and have dealt with a lot of flaky weird guy behavior, but this has completely thrown me!