Please try not to worry OP. I remember feeling like this in my first pregnancy. The baby was a really abstract concept to me. I just couldn't picture him and I found the whole process of pregnancy very odd, like my body had been taken over by an alien. What really helped was picking a name, we chose it after the 20wk scan and called him by his name from then (though we didn't tell anybody else). When he was born I didn't get the instant rush of love (difficult birth) but I felt very protective of him, and by about 6 weeks I loved him so intensely I can't describe it. So please don't worry, how you feel now does not necessarily indicate how you will feel when he's born. It's a good sign that you are excited when he kicks, and that you are starting to make preparations for his arrival.

Your DPs family sound a nightmare, at this point they should worried about YOU, the baby can wait until it arrives. And now might be a good time to start laying down the law with the MIL, if you are worried about PND (is there something in particular that's making you worry about this?) then the last thing you want is someone riding roughshod over you and questioning your parenting.