Is your baby gaining poorly? How does he sleep? If he is gaining within normal limits, not keeping you up all night, not abnormally fussy or in pain, I'd say you don't have a problem.
Normal bf stools can be yellow and curdy to green and slimy. Many babies have lots of gas and are totally normal.
Many babies need to nurse extremely frequently--12 times a day is roughly every 2 hours--normal for a young baby. Even my 2-year-old dd has been known to nurse as often. Give yourself a break from watching the clock and watch your baby instead.
There really is no such thin as "too much milk." Your letdown is probably quite strong, you have an easy time pumping, and your breasts are not used to making milk yet and may become full-feeling and leak. Again, you sound fine to me. If your baby is irritated by a strong letdown, try hand-expressing a little milk before you nurse, and latch him on when the letdown slows down.
When I say. "express a little milk," I do mean "a little." The same goes for when you are feeling full. If you pump to relieve fullness, you're telling your breasts to make more milk then the baby needs. If you nurse him on demand, your body will adjust to his needs.
Some babies nurse for hours, and some nurse for minutes at a time. Your baby is probably a very efficient nurser, provided he's having many wet and poopy diapers each day. It sounds like making dirty diapers is no problem for him
My dd once pooped all the way up to her hair!
Enjoy your little one--they grow up fast.