how to get things done when your so sleep deprived

This morning I was so tired when baby girl woke up that I put her on the boob and back into her bassinet .. no burping , no diaper change ... I feel like a terrible terrible mother .. after 20 mins of her gurgling i got up and burped her and change her diaper but now I'm sat here just in tears for simply how tired I am! How am I sposed to be a normal human being!?!? She's 7 weeks old! How on earth are some ladies back at work!?!?