I have had this before, and the more I dreaded the sensation the worse it was. I think I was just tense and putting too much emphasis on "the task" of intercourse and not enough on lovemaking, so my suggestion to you (which worked for me) is buy a lube/massage gel (durex do a nice 2 in 1) and have lots of fun. Concentrate on the foreplay and not the actual intercourse and you will most likely find sex just happens and is a lot more pleasurable.