Jesuis it sounds like a combination of alcohol and nerves. I have dated two guys in the past who had this problem at the start, and it resolved after a month or so.
Well my sleepover with Mr Outdoors went very well. We ended up getting a bit drunk at his in the afternoon and went to bed rather early. It was good fun although more of the drunken fumbling sex than amazing quality. Mainly due to our drunkenness than any lack of skill on either side. And his equipment definitely works! We didn't dtd in the morning as his neighbour was doing DIY and knocked on his door to borrow stuff and it was a bit of a passion killer. But he was very sweet and brought me two cups of tea in bed (Mr Outdoors, not the neighbour 
).
We went for a drive in the countryside this morning and had a pub lunch, after which he drove me home. Unfortunately one of my cats had decided to punish me for staying out all night and had peed and pooed in my living room which ruined the rather romantic/sexy plans we had hoped for. She has a littler tray for God's sake, and a cat flap! It was extremely embarrassing and he rather wryly told me that I had managed to dissuade him from his plans to get a cat!
We are going to meet up mid-week and have another sleepover next weekend. I managed to avoid asking him if he was dating anyone else as I would be surprised if he had the time, and anyway I would rather wait before having the 'exclusive' conversation. It gives me a bit or leeway too, in case I feel like meeting up with someone out of curiosity.