DD will be 7 weeks on Thursday. Even before my postpartum exam last week that gave the ok for sex, DH and I were already discussing the idea of trying for our next one. We want a big family (big as in 4) and don't want to be too old when we have our last one (we are both 29). I'm excited at the idea of adding to our family and don't mind starting to try sooner rather than later (it took 7 months with DD), but I was wondering how soon did any of you decide you wanted another child? I'm just curious if this is post baby euphoria or a somewhat normal thought process for someone who knows they want more kids.
BFP #1 7/6/2012, EDD 3/13/2013, Delivered 3/14/2013
BFP #2 1/7/2014: EDD:9/14 MC: 1/9/2014 (confirmed via blood work)
BFP #3 7/5/2014: EDD 3/11/2015 MC: 7/15/2014
BFP #4 11/7/2014: EDD 7/17/2015~~Please be my RAINBOW!
My Chart

All are Welcome!
Re: Thinking about the next one...
TTC#1 for 19 months with PCOS and MFI IUI#3 + injectables = BFP!!!! Beta#1-134(13dpiui) Beta #2-392(15dpiui)
#1 born December 2011
TTC#2 - Beta #1 -51@10dpo Beta#2 -1353 @16dpo
#2 born May 2013
TTC # 3 June 2014 BFP 12-1-14
#3 born August 2015
#4!!!!!!! due June 2017
DH and I knew immediately after our 1st that we wanted a 2nd. We originally wanted them 18 months apart, but we miscalculated and got impatient. We stated TTC when our 1st was 4 months old and got pregnant the 1st time. That meant they would be 15 months apart, but then DS came 5 weeks early and they are 13.5 months apart.
We don't regret it for a second. The age gap works perfect for us and we are glad we had them close together and got the sleepless nights over with quickly. Soon to work on potty training, then that will be out of the way also.
In most cases I would say its baby euphoria and happens to lots of women. In your case you have some seemingly rational reasons to want to have another child sooner than later. It was the opposite for me-we had planned on kids close even before I got pregnant the first time. When my oldest was a newborn I said I wanted to wait a while to which dh said we should stick to our original plan. In hindsight I am really glad our kids are so close in age. I feel like the benefits far outweigh the challenges.
good luck with whatever you decide!
You sound like DH and me. We want a big family (4-5 kids) and were 29 when dd was born. We never prevented after her, but since I was ebfing using lam guidelines, we expected that it might take us a while to conceive. It didn't. We got pregnant faster the second time around, so DD is getting a brother when she is 13.5-months-old. At first I was a bit overwhelmed, but now I'm super excited. It helps that DD has grown up a lot since my bfp.
I cannot say if your thought process is normal because I doubt I'm ever very normal in my thinking.
However, we're happy with our decisions. Do what is best for your family and enjoy doing it. 
Ds 1 and DS 2 will be within a week or 2 of 12 months apart based on when they schedule my rcs. I wanted a close gap between them, but was thinking more of 18 months, so I opted not to go on BC.. We got our surprise bfp shortly before DS turned 4 months! First tri was a little tough just because of exhaustion, working full time and having a 4 month old, but I actually think now, in third tri, it's more difficult. As PP mentioned, DS is starting to be more mobile/active, but not independent enough where he can get around on his own.. This means we spend a lot of time holding his hands walking him around and such.. Bending over like that definitely takes a toll when your carrying extra weight in the front anyway!! Plus, holding him wears me out.. We were just at the doc today because of spotting, which they are guessing s frm over doing it carrying around a 9 1/2 month old.. It's tough, but we are still super excited for what the future holds and so anxious to meet this next little one!! Best of luck to you!!!