I might have screwed up

So I slept with my boyfriend yesterday... like any other day! while we were having sex he went soft... so I got off him and irritated by it i said "always" under my breath. he hears me and was so offended. I think I might have literally broken his heart. It does happen a lot though and he always makes it weird. He says it's because he's got a lot on his mind. How do I get him to be in the moment and enjoy it and not be insecure about him going soft on me?