M.G.
I breastfed my twins exclusively, and we ended up making it all the way to 15 months. When I went back to work they were only eight weeks old. My supply diminished quickly, so there were some tricks I did to keep it up. I was given a prescription for Reglan (my lactation consultant said the herb Fenugreek wouldn't be strong enough for me since I was feeding two). I took that for six weeks and it helped. I was told to pump after each nursing session, but I was just too darn exhausted to do it, plus one of my babies always needed me. There just wasn't enough time in the day.
I did do the breast only approach. This is truly the best way to increase your supply. I was able to breastfeed twins, which meant I had to produce enough milk for TWO babies. I was so shocked I was able to do it, but I always fed them from the breast, unless I wasn't home to feed them.
You can find information out there on different websites about what you can do to help keep your supply up. Also, talk with a lactation consultant in the hospital after your baby is born. Share your concerns, and you should get some great advice.