You need to eat well for you as well as for the baby, so although the baby will take what it needs from your reserves if you want to maximise your ability to bounce back after the birth looking after your body is essential.
I guess your MW can advise on weight gain, and reading up on the nutritional requirements in pregnancy will help you ensure that you are not run down, or lacking any nutrient that might adversely affect your recovery post delivery. I have found the 9 months of eating well chapter in 'What to expect when you are expecting' very helpful. A rough summary:
daily:
3 protein servings
4 calcium food servings
3 vit C food servings
3-4 leafy and yellow veg / fruit servings
1-2 other fruit/veg servings
6 or more whole grain (e.g. wholemeal bread, cereals, rice, couscous etc) and legume servings
Some iron rich foods
approx 4 fat and high fat food servings
at least 8 x 230ml glasses fluid
plus a prenatal vitamin supplement
Things can double up e.g. 3 x 230ml glasses of milk = 1 protein and 3 calcium servings
I was surprised at just how large some servings were e.g. 4 eggs = 1 protein. That's a lot of eggs....
I have gained more weight than you, but no wobbly bits (!), have no morning sickness or other aches and pains, am not particularly tired, and have lots of energy when exercising. I put this down to eating well. I am lucky enough to have a personal trainer who gave me an absolute rocket about not eating enough, or properly at the start, and who made me keep a food diary. I am very grateful for that rocket 