hello, when we moved DS1 into a bed, he was just under 2, and we had exactly the same... I was pregnant too, so know what you're going through. I think it's a huge change for them, moving from cot to bed, and it's also really exciting, so it takes time for them to settle down, esp if you have to do it earlier than you'd really like (i.e. if you need the cot, like you do and we did!)
How long ago did the move happen? For a couple of weeks afterwards, I had a nightmare re. naps, and DS would scream, get up and down, throw nappies around the room, etc. I knew he still needed the nap, and it sounds like your DS still needs his too, so I got tough after spending a horrid few days putting him back in to bed whenever he got out (that quickly became a game that could have gone on all day and night...!).
Luckily our door handles are v. high so he can't open the door (but I have held the door shut with a broom handle at his grandad's house ...) At nap time, I'd take him up, put him in bed, say nap time, kiss him and leave. The first day, he went up around 12.30, and he stamped about until 2, before going to sleep finally. I went in once to check he hadn't done a poo while he was moving around (he had a tendancy to do that), but that was it. I woke him up again at 3, i.e. normal time. The next day, it was a shorter period, and by 2 weeks, he was back to getting into bed fine and sleeping for anything up to 2 hours.
Around the same time, he did start being scared of the dark as well, so we got a little nightlight - one of those tiny ones you plug into a socket. That helped at night.
I reckon it was about 6 weeks before he settled properly into his bed, and I'm sure it would have been longer without the "tough" approach at nap time. Now (9 months on) he's good as gold again, and has been for ages (although the lunchtime nap has sadly gone... ).
Sorry this is so long, but I remember being in floods of tears, listening to DS stamping in anger and shouting... I really feel for you, and hope that you can sort it out.