Yesterday I had 17 follicles on the ultrasound. My E2 was 333.
E2 is supposed to be 200 for every 1 egg, right? I am trying not to stress...really I am. RE wants me to do three more rounds of stims (last night, today, tomorrow) and go back Sunday. Since my largest follicle was only 12, everything is okay, right? Right?! 
Me: 28; DH: 35
1/2008 -- Started TTC
3/2009 - FD discovered at 17 weeks1/2011 - Lap and HSG reveal Stage IV Endo and both tubes blocked.
4/2012 - Consult with RE for IVF#1 - Labs and SA are normal - Repeat HSG - SURPRISE! Both tubes are open.
May, June, August 2012 - IUI#1-3 - Letrozole + Bravelle + Ovidrel trigger = BFN
9/2012 - Lap#2 to remove endo and Hysteroscopy
IVF#1 (Long Lupron) - 12/6 ER - 20R 11F * 12/11 ET - Transferred 2 excellent blasts * 3 Frosties *
Beta #1 79.7 * Beta #2 240 * EDD - 8.29.13 * It's a GIRL!

Re: E2 vs follicle count
It's 200 for every mature follicle and since you don't have a mature follicles yet I wouldn't be too concerned. What day of stims are you on? Have they upped your dosage at all?
GL to you!
bump burp!
My understanding is 200 for every mature egg, so with 3 more days of stims that's still plenty of time for them to mature and raise your E2.
The other thing that I've heard is 2mm for every day of stims, so if that was day 5 (I think you're a day behind me?) then you'd expect most of them to be in the 10 range.
This is my first round of IVF so most of my info is coming from Dr. Google, so other women here may have more accurate answers than I do, but it sounds like you're on the right track!
At the time of the lab work, I had completed five days of stims. I am on 300 iu of follistim and 75 iu of menopur, plus 10 iu of Lupron. That's what I started with and that's what I am continuing with.
Thanks everyone for all the reassurance! IVF is stressful!
Me: 28; DH: 35
1/2008 -- Started TTC
3/2009 - FD discovered at 17 weeks1/2011 - Lap and HSG reveal Stage IV Endo and both tubes blocked.
4/2012 - Consult with RE for IVF#1 - Labs and SA are normal - Repeat HSG - SURPRISE! Both tubes are open.
May, June, August 2012 - IUI#1-3 - Letrozole + Bravelle + Ovidrel trigger = BFN
9/2012 - Lap#2 to remove endo and Hysteroscopy
IVF#1 (Long Lupron) - 12/6 ER - 20R 11F * 12/11 ET - Transferred 2 excellent blasts * 3 Frosties *
Beta #1 79.7 * Beta #2 240 * EDD - 8.29.13 * It's a GIRL!
When Not IF Blog
Everyone welcome!
First mini-IVF Sept 2011... Only 1 egg! ... BFN
Switching RE
IVF#2 May 2012 9 eggs and only 2 sperm, WTH!
BFN
Switching RE's within practice
*~God gives his hardest battles to his toughest solders. Unknown.
Your E2 will start rising quickly as your follies get closer to maturity. (My E2 was doubling for my every other day monitoring appointments towards the end of stimming.)
TTC since 10/2010
IUIs # 1-5 = BFFN
IVF # 1(July 2012) = BFN
IVF # 2 (November 2012) = BFP (MIssed MC D&C @ 8w3d on 1/10/13)
Our beautiful babies
If your largest was only a 12 then that e2 doesn't sound too low. You probably have a few more that just aren't large enough to be measured properly. My e2 for my last round ended up being like 166 per mature egg so just keep stimming and take a deep breath
Good luck!
NTNP 2009-2012 TTC since 2012:
Jack has handpicked his sibling up there
My blog about IF and loss ... Kate's IF Blog