You two have only been in a relationship for 6 months, he's never been in one that long, I'm sure he had no intention of becoming a father and co parent with someone he hardly knows. Despite of what he says, he is probably not feeling this whole relationship thing. With a child coming, you two will be connected whether he wants it or not. This may be the sign of things to come.
Have him go to the doctor with you, let the doctor tell him that sex is not taboo during pregnancy. My feeling is that he no longer wants this relationship. I hope you two will find a way to work this out.