It sounds like you are letting your head/imagination in there too much. I remember when I use to think about praying when I was going to the bathroom, for example

The key to intimacy is to already be good friends with yourself so you aren't embarrassed by yourself. You can laugh at yourself and your mistakes and don't take them "personally" (that they reflect upon you). Stumbling while praying, for example, not being able to find the words; if you get hung up on the "Other" person who is listening and what they're thinking, etc. -- it's not like that.