It's because for some people, blood will start flowing a lot to your vagina and it can swell up, it's not harmful or anything, but can be a bit uncomfortable
I get sore and swollen after too. He hasn't mentioned abt me being tighter but it feels tighter to me.
This happens to me too, except when were having sex is really painfull and afterwards I will get really swollen... And ofcourse he will become active. Im 28 weeks... and I feel hella weird because I feel like he knows what were doing... bit akward lol
All of it is totally normal! ;-) I tend to be much tighter down there as well, and my hubby asks if it doesn't hurt me, since its extremely tight around his precious...lol. It can hurt a bit afterwards, depending on how rough or long etc sex was. During my first pregnancy my daughter used to kick a lot during sex which was really weird lol...so yeah...its all normal, don't worry about it. It just can be a bit distracting sometime :-P