For me it was mastitis, hands down the first bout. The second wasn't as bad because we caught it right away.
In second place was when I had the flu when I was 27. That was brutal.
For something noncommunicable it was my anemia. I couldn't walk up one flight of stairs without thinking I was dying.

Then and now. How did my boy get so big?
Re: What's the sickest you have ever felt?
Official Due Date 5/29/15 & HB 143 on 10/13; 11/25 Harmony Results perfect & it's a Girl!
Off BCP 5/2009
TTC since July 2010
DH's SA = Normal!
Hysteroscopy 2/2011
50mg Clomid / Progesterone 77.5 April 2011 = BFN
25mg Clomid / Progesterone 53 May 2011= BFN
25mg Clomid / Progesterone 44.3 June 2011= BFN
5mg Femara / Progesterone 15.7 July 2011= BFN
5mg Femara / Progesterone 14 August 2011= BFN
5mg Femara + Crinone / Progesterone 32 September 2011=BFN
5mg Femara + Crinone / Progesterone 14.9 October 2011=BFN
First RE Appointment 11/2011
Hysteroscopy 11/2011 & on Med break
12/2011 Diagnosed with PCOS (Insulin Resistant)
12/2011 Adding 1000 MG Metformin per day
12/14/11 BFP
Beta #1 664 Beta #2 3330 Beta #3 6160 Beta #4 19546
Official Due Date 8/18/12 & HB 147 on 1/3; HB 171on 1/19
Pre-term labor @ 29W bed-rest till Emergency C-Section
IT'S A GIRL
As if I didn't feel bad enough, my boss was not sympathetic and told me to come in anyway. I did but my boss's boss saw me, told me I looked like hell and sent me home, but not before talking to HR to help mediate the expectations of my boss (who was promoted to another store while I was gone so thankfully there was no awkwardness when I came back). Oh and the illness jacked up my period so I also had my one and only pregnancy scare. Joy.
___________________________________________________________________________
Trying for #1 since May 2010 l DX ~ Unexplained Infertility June 2011
IUI #1&2 = BFN; IUI #3 = BFP, m/c @ 6 weeks
November '11 ~ IVF#1 ~ ER 11/18 (29R, 17F) ~ 5dt of one beautiful blast on 11/23 = BFP!!
Beta #1 9dp5dt = 116, P4 = 28 ~ Beta #2 13dp5dt = 700 ~ Beta #3 20dp5dt = 9500, P4 = 26
1st u/s 12/27 - hb of 156!! EDD 8.10.12
**TEAM GREEN!**
Sweet baby boy born 8.18.12
Trying for #2
FET #1 - October '13 - c/p l FET #2 - December '13 - cancelled
l FET #2.2 - 1.30.14 - BFN
~ More testing - hysteroscopy, endometrial biopsy & more b/w - all normal / negative~
Surprise BFP while waiting on FET #3 ~ beta #1 500; beta #2 1600; first u/s 4/3 - measuring 5w5d, no hb yet!; 2nd u/s 4/10 - hb 132, measuring 6w6d - EDD 11.29.14
**TEAM GREEN!**
Beautiful baby girl born 11.24.14
1999- Dx Prolactinoma
8-25-2012 - Lucas born via C-section at 38 Weeks 2 days
Second was a gall bladder attack.
My first scuba dive. I suffer severe motion sickness and lost my lunch off the back of the dive boat, it was a really rough water day and I couldn't keep anything down.
I used to get stomach aches so bad that I couldn't stand up or lay down. I was working retail at the time and my boss didn't believe me. She was on maternity leave when they realized that these stomach aches were caused by two large cysts. One was the size of a large watermelon and the other one roughly the size of a honey dew.
Second place was the flu, Christmas 2011. It was compounded by the fact that I was newly pregnant and throwing up a lot anyway. It was terrible.
That's horrible you had such an unsupportive nurse.
OMG, WTAF, this!! That lady should be fired.
At that hospital they all thought I was on drugs and seeking attention. They discharged me the next day when I still wasn't conscious and couldn't walk. I think it started with the paramedics who thought I was attention seeking. My sister has seen before where paramedics influence how the nurses treat a patient. The second hospital I went to 3 days later figured it out and all the nurses and everyone were amazing. Nurses are my heros, you are all amazing, I won't let my experience with a few bad nurses to skew my view. I saw how hard you nurses work, thank you.
It's a tie between having mastitis last year and the flu when I was 17.
My high school teacher took us to Canada during Feb. vacation and I got sick with the flu. I had a horrible fever and nothing to take to help bring it down. My best friend (still is to this day) had a bucket of ice and kept putting cool face cloths on me to help bring my temp down. Luckily the day I started with the fever was our last day there. The bus ride home sucked.
The mastitis sucked too because the first round of antibiotics didn't work. After 3 days of taking them and my fever/pain not going away at all they gave me something else. Luckily my MIL had the week off and helped out with the baby.