Hi A.! :)
It should be noted that you shouldn't be drinking any Mother's Milk (or other lactation teas) while you are still pregnant. They contain herbs that are not good for you *or* the baby right now. Only drink them *after* you have given birth.
It can take anywhere from three to 7 days for your milk to come in, and as far as I'm aware, the only thing you can do to make it faster is to let baby nurse as often as they will. Babies *will* suck almost 24/7 during that initial period to get all the colostrum out, but it also stimulates your milk production (also making for a *great* supply!).
Very few women actually have a low supply, and in the initial period make enough milk for twins! Baby wanting to eat all the time does *not* mean you have a low supply. Watch diaper output - not enough wet/dirty diapers would be the first indication of low supply. (And keep in mind that breastfed babies can go as long as a week or more in between bowel movements after the first 5 days!)
If, after watching all this, and baby loses more than 7% of his/her initial birth weight, and you really feel it's possible you have a low supply, try taking herbs such as Fenugreek or alfalfa, or eating lots of oatmeal. All those can help. Also, do a google search for "Housepoet's Lactation Cookies" - those work like a charm and taste great!
The first 6 weeks really are the hardest (I've gone through this three times now), but after that, it's like someone pushed a magic button! It gets sooo much easier. The first 6 weeks, it really will seem like baby does nothing but eat - and it's probably true. But it's great for baby, and it's great for you as it helps your uterus get back into its proper shape, and helps you to lose that pregnancy weight!
So hit up the library and get some good books for you and baby (and your 2 year old!) to curl up on the couch with for this time period.
As other moms have said, pain shouldn't be an issue. Most often, it really is a latch problem, and you should see an IBCLC (International Board Certified Lactation Consultant), or contact your local Le Leche League. They will be the most help to you.
That said, for some people, it really does just hurt. With all three of my munchkins, I went through the pain, cracked nipples, etc. for the first 6 weeks, and their latch was perfect. But again, after the 6 weeks - *no more pain*. So don't give up - though I know it can be so hard - find a support group. And don't offer bottles or pacifiers - those will only hurt more than they can help (by affecting your supply, and by changing their latch). If you really are having problems with pain, as a last resort look into getting a nipple shield (they sell them at Babies R Us) - but use it sparingly. It can be difficult to wean a baby off of them as they get used to the feel. (I've only used one with my last, but fortunately she had no problems going back to only breast.)
A great resource for breastfeeding is http://www.kellymom.com. You can find any answer to any question there. And please don't hesitate to email me either! My email is kaffine23 AT hotmail DOT com.
Wishing you and your family all the best :)