Sounds a bit like my dh too!
Perhaps we have lost our mystique!
Children change and grow, they are interesting and give love and smiles to those that love, care and nurture them.
They don't ask 'how was your day?', they show you treasures from the garden.There's always something new to observe in them.
Seeing how lovely dh is with the children reminds me of how loving he can be, even when he is being distant, stand offish and appears to be pushing me away. I definately have had the feeling that DC's rule in dh's eyes and spontaneous affectionate love appears to be saved for them. I have been jealous and probably cross particularly with ds at some points in our life together so far.
I think you need to stop the bed swapping business before the baby arrives because there could be some resentment of the change in situations by your older 2 if the new baby seems to be the one who changes their bed time arrangements.
What you need to work on is you, what makes you stand tall and proud, interested in life around you. What attracted you to each other in the first place? Can you find some time to pursue your own interests?
Also are you a romantic - do you notice when others seem to be holding hands and not you? Do you watch a film, read a book and visualise your relationship differently? Remember it's fiction.
I know people who paint marvellous pictures of their life, they have rosy tinted glasses and good luck to them but I know for a fact they dont't have that perfect marriage or those ideal children etc etc.Perhaps they try to keep your glass half full as we all should. Dwelling on failings will not make them better it only serves to get you down, I know that.
Do you dislike or resent his behaviour and therefore find it more difficult to get close to him as a result? Perhaps it's time for you to be more physically attentive in the relationship, he's tired, he's working hard, relax him!!It does not have to be sex.
Heaven knows, you'll need relaxing in a few months!
Sorry this is a long post, I do know where you are coming from and have experienced this - and still do sometimes more than others. Bridge the void and keep positive about yourself.
Positive vibes your way.