I really don't think it's that big a deal in such a short span of time as six weeks to experience a few sexual liaisons that don't seem as great in comparison to previous times. I mean, really, six weeks is nothing. Now, if the sex is mostly bad over a long term, like several months, that would be something to indicate it's going nowhere. But at this early stage, it's no big whoop. Everyone has an off night, and people don't always connect the same way every single time they get together. It sounds like you two have lots of other cool and positive things going for you, so I wouldn't write him off yet if I were you.
The world opens up... when you do.
Oh, oh, can't you see? Love is the drug for me. ~Bryan Ferry
"Love is that condition in which another person's happiness is essential to your own." ~Robert Heinlein