I got pregnant with my second child 6 weeks after having my first - and it wasnt an accident! I found it OK in the first trimester as I didnt have m/s but I was tired and I did have to ask for help at times from nearest and dearest. I found the third trimester very hard, as i didnt drive and i had to catch buses everywhere whilst heavily pregnant, clutching a stroller and a child under a year old whilst experiencing the most annoying Braxton Hicks which made my stomach feel like a rock hard football. Lovely.
Seriously, though, just try and rest when you can and ask for help. And make DH do the housework.