At first I was breastfeeding then I was nervous he wasn't getting the amount he needed and my book actually became blistered and engorged. I was so desperate to get more/fast milk that I ended up resorting to pump feeding. I will have to try a sling carrier as you suggested I feel that that would work great for breastfeeding. I have an appointment to see the lactation consultant on the 4th but I must say I'm nervous.
A friend told me about some cookies you can make that improve your supply. Maybe look it up, I don't have the recipe.
Were you just pumping with your first or were you latching him on as well? If you were able to pump a little but felt very engorged afterwards it wasn't that you didn't have enough supply - it's that you weren't able to get it out effectively. Talk to a lactation consultant, find a local chapter of La Leche League. It will help immensely if you have someone working with you in person one-on-one to make sure you have a good effective latch. Many women aren't able to pump a whole lot but have plenty of supply, they need baby to be latched to get a good let down. The best way to build supply is to nurse a lot and to keep your stress level down.
Have you looked into a good baby carrier? Slings and wraps can be tied in such a way that baby can be skin-to-skin with you while you're up and moving around (chasing your bigger kid) and the support means you can nurse baby (once you get the hang of it) with only one hand occupied. Crotch-dangler carriers like infantino and baby bjorn aren't good at all, but once baby is out of the newborn stage (when slings and wraps are best, check out Moby wraps and Baby K'Tan carriers) then soft structured carriers are also good (like Ergo, Kinderpack, and Boba).
You have to pump for 100 minutes per day ( 10 times per day for 10 minutes) hand express while pumping, to boost supply (Google stanford hand expression). Mother's milk tea can help to boost your supply (3-5 cups per day). You may want to look into baby wearing, that way you can nurse and have hands free for your older child.