So you know - the let down pain and some of the leaking does to go away. It just means that your breast are getting use to working so much. The only time I feel the let down or leak is when I miss a feeding or he goes over 4-5 hours with out nursing.
Babies do go through cycles - growing & not growing spurts. They will nurse more when they are going through a growing spurt. My youngest is about 11 weeks now - almost 4 mo. He sometimes wants nothing to do with the 2nd side. I had to start wearing a braclet on my wrist to tell me which side he was last on, cause I couldn't tell & was forgetting with everything going on. But most of the time - he wants both side.
As to knowing if she is getting enough... does she seem full and give up the breast on her own? Does she go atleast 2-4 hours between feedings? Does she have 6-8 wet diapers a day? If so, she is getting enough. If you are still worried about it, you can call the doc & see if you can bring her in for a few weight checks... that way you can watch her weight gain & get individual suggestions.
Also, if you think your supply isn't enough - you can let her suckle a little more or pump after she is done feeding. Even if it's just a few minutes on each side. When my little guy was just about 2 weeks old - I had to spend 5 days in the hospital. My supply did go down & his need went up when were apart. It did take a few weeks, but we did get to where we could just do his feedings from breast again. But I was lucky cause I could use the milk I pumped at the hospital when I returned home & during the supply rebuilding time.
I have also notice that oatmeal helps with milk production - not sure why, but it does. When my guy is going through a growing spurt I try to eat it for breakfast, late night snack & I even eat oatmeal cookies for a mid-day snack. I just use instand - eventhough somepeople say it doesn't work. But it did for me... and this is the second one I've done it with.
Personnaly - I don't drink when nursing, but I don't think once will hurt her. That is also something you can ask the doc about... I know I had one drink w/ my 5 yr old - that is before I knew he was on the way. And I was told one wouldn't hurt in anyway. But it never hurts to ask.
Good luck with nursing... and congratz on the little one :)