Hi sistarosa- welcome to BH
Firstly- good on you for wanting to fully bf your boys
I think the best way to help build up your supply would be to reduce the amount of formula you give the boys and put them on the breast as often as possible. I wouldn't take away all formula full stop, as it is placing a great strain on you to suddenly DOUBLE or more the current amount of milk you are making- and stress isn't great for BF'ing.
Think about your diet too- there are foods out there great for BF'ing and ones that aren't so good. Drink PLENTY of water all day (and even sips through the night if you wake up.)
Oats and yeast are great for boosting supply, and there is a recipe in the BF section of the forum for lactation boosting cookies that use both these ingredients- they are SOOO YUMMY! (And yes- they do work, so get onto them- if you can't cook, find a friend who will be willing to help you out. Or even, read the whole thread because there are a few variations other members have made to the recipe to include all the good stuff but make it easier, such as using a packet cake mix )
Hmm... what else can I think of?
It's never too late to build up supply- oh, if you have a health food store nearby pop in and grab yourself some fenugreek OR blessed thistle tablets- they also help boost supply. (I personally went the blessed thistle as I had heard fenugreek can give you stinky breath! )
Hope that helps- and if you need further information don't be afraid to ask