We have 3 kids: 17g, 15(almost 16)b, and 9g. The oldest two are 17 mos. apart, and the middle and last one are almost 7 years apart.
While not even having the first one out of diapers before the second came along(she was *almost* there, but then regressed when the baby was born) was hard, it was in a way just as difficult when the 3rd one was born, even with almost 7 years diffference. It was a huge culture shock for me, and not at ALL like riding a bike(you most certainly *can* forget things, and each child is sooooo different from the others).
After I had my first, I desperately wanted to have another, and just when I stopped wanting to get pregnant, WHAM!, there I was. After having him, I wanted to wait awhile, so I got on Depo, and that messed me up for quite awhile, so badly in fact, that I didn't think I was ever going to be able to have children again, so I pretty much accepted that I wasn't going to. I had one of each, and I was content with that.
When my son was 5, I was having some medical issues. Not life threatening, but they were of a concern, so I went in to get treated. The suggested treatment was a fertility drug so that things would get back to normal(not so I could get pregnant), and we were counseled that I could become pregnant with multiples. All of a sudden, we were faced with the possibility of not just two children, but maybe 1, or 4, or 7 more. We talked and decided that for me to get better, we were willing to risk not only a pregnancy, but possibly way more than one baby. Thankfully, we only had one.
Although we were content with two, obviously the "divine plan" was for us to have at least one more, and even though our two youngest are so far apart and it was like starting over again, our family is the way it's meant to be now. Sometimes I want another, but then I remember all the individual challenges we had with each one, and how dramatically it would change life now, and how all consuming a baby is on life, and I decide a brief baby fix is enough for me, to "oooh" and "aaahhhh" over someone else's will do just fine. I love babies, but deep down, I don't want another of my own. Nobody else in the family does, either, not even my youngest, not even when she was 3.
I think for you, you should think about all the ways a baby would affect you, your family, your life. Someone else did pros and cons. That's good, or just look inside yourself, and think about if it's really what you want. Definately, it's something you and your husband should decide.
If you *did* do it, I'd suggest waiting until the youngest is in school at least half day, like someone else suggested. You have more time to bond with the baby without someone else getting jealous(and yep, it will happen), and in the evenings, your husband can help, as can the older children, with the baby, so that you can rotate individual quality time with your other family members.
Whatever you decide, it seems like you have a wonderful family life right now. Children are a blessing rather they're the first, third, or 6th.
Good luck with making your decision.
K. W