I am 35 weeks and havent had any trouble sleeping with this preg because i havent taken any naps. I sleep great at night except for the accasional getting up to pee. I feel great during the day. With my first preg i slept a lot and it made me miserable and more tired. You should rest more during pregnancy but sleeping too much will make you more tired. I have come to find out that the more active i am the better i feel.
I think everyone is very different but at around 13 weeks i started to sleep better... thru the night (up once to pee) and sleeping about 9-10hrs with no naps during the day. Now...20 wks...back to crappy sleeps and tired thru the day. Can't get comfy in the night now...belly is too big! Just rest as much as you can...you need it! Building a little person is a lot of work!