You're not spoiling him.

You cannot spoil a baby less than two months old. The tool I most recommend is a sling or a harness carrier like a Snugli or Infantino. Either one will let you easily take a walk why your baby naps. An Infantino is much simpler to get the hang of, but a sling is more versatile in the long run. Your hubby can watch the older kid(s).
Other than that...Make sure you're eating enough. You can most likely eat about 1800 calories a day & still lose weight. Make sure you eat the right things
for you, something you're really only going to find out through trial and error. Generally speaking, though, fiber and protein will help keep you full longer, so try to make sure your meals incorporate both. If you don't eat beans often, they're a worthwhile addition to your diet. A half-cup serving of vegetarian (fat free) refried beans has 100 calories and about 7g fiber. Being from Texas, I know they even go with breakfast.

Other beans are comparable in calories/fiber and I have found them to be about the most filling thing. They're cheap too.

Just a thought...