Hihi, your mum is right, you should rest as much as you can now since there is someone helping you with your baby. When I had my 1st child, I'm also like you, didn't lie down n rest much coz anxious about baby, after awhile I began to have constant backache and it got worse when after my confinement coz I need to take care of baby myself. Not enough rest time, constantly on the move and after my maternity leave ends, I gotta go back to wrk which means sitting in front of the comp most of the time. And also after giving birth our womb tends to be lower than before, that's y older pple always tell us dont walk or stand too much. My massage lady did help me to push back the womb n tell me the same thing but I didn't listen so in the end my abdominal will pain frequently. And I dont know issit due to this that I had a tough pregnancy the second time.. My abdominal is always painful and towards my last trimester I cun even get up without much hassle so in the end I request to induce hoping the pain will go away after my 2nd is delivered.
Thus this time round I make sure I rest as much as possible and I had just ended my confinement and I didn't feel as bad as before.