I've delt with this on and off for about 4yrs! Always said when youngest starts nursery school if we were going to have another it would be then. Well now is that time, like you some days I've wanted nothing more, I've been in tears over the thought of not having another (must of been hormones!) however I think I like the sound of it (the nice bits) more than the likely reality. My partner has always been no more, however has now said he will be ok for another if it's what I want. It seems each time we get close to going for it I back out. I worry about all the hard things of three and of having a baby/toddler etc full stop. I've come to realise I want to stick with our 2 boys, I like our life, I like having time for me and holidays, I don't want to go back to sleepless nights and I'd feel hugely guilty not been able to do family activities due to a baby. We're just approaching a really fun stage at almost 7&4, time for trips to the cinema, ice skating, bowling etc etc we wouldn't be able to do these things with a baby, or one parent would have to sit out which dosnt seem as much fun. I'd feel as though I'd be holding them back and stuck in the baby years for another 3 years, when we're all moving on together. Plus my career is good right now, I was the only one who really wanted another baby, maybe a little selfishly, yes I would of liked to of got to experience having a daughter but I'm ok with it. I think I get on better with boys anyway, teenage girls are abit scary! (But guess if your in that postition you just deal with it like everything else) I feel at ease with my boys, I know what I'm doing and they are also good friends, play together, can go to a theme park to suit them both, share clothes, play computer Games together. It's great and getting even better. I love my kids more than life itself and we have lots of fun, but kids are hard work! And expensive! You have a choice do you want to deal with it all again? And all the additional things 3 brings?
I no longer feel the need to do it all again, I used too, in the early months after having my 2nd for a while, but I just think I'm past that now, we've come too far to go back, wouldn't feel right going to the baby groups again, I've been there done that, it's time to move to the next stage that we haven't yet experienced as mentioned above. I also often feel relief whilst sympathising! when I see people struggling with a 2yr old etc that I don't have that anymore, although our 3yr old can still have his moments!
And relief when I want to book a weekend away or holiday, I think now I'm glad we only have 2 as it's so much more for a family of 5, same goes for clothes shopping for them, could go on! Plus the thought of 3 terrifies me, we can handle 2 well, think 3 for us would be stressful. I like that one of us can take them both, my partner is bathing them and putting them to bed right now, and not been overwhelmed or too stressed out, the other gets a break. I can't see that with 3, I don't want to be resentful when I'm 'stuck' with a baby and the others are off out having fun etc yes having a little baby is fun for a while, but not so much if they've not slept all night or have colic, constipation or whatever. I can just imagine that's how it would go, me and the baby and the boys with their dad... I'd rarther be having fun with them
So my current family, along with practical and financial/lifestyle reasons I've decided to not add anymore children to our family. And I actually feel good about it, feel like I can move on, concentrate on the family I have. Yes I'll wonder what it may of been like and get the odd pang that's natural but I can't imagine going through the hard stuff again and altering our family, for us I know it's the right decision. I just need to decide on some contraception now!
So I guess it comes down to what you want, what sort of lifestyle do you want for you and your family, are you sure it's not just hormones. Think you really have to honestly think about it, I worked out potential costs and priced up holidays for 3 and everything before deciding, we could actually afford it, even with the 5* abroad holidays (Saying that if we ended up moving to a bigger house things may be different then with a bigger mortgage and household bills and if anuthing happend with work) do you honestly think you could manage physically, emotionally and financially, do you have family support (we don't have much and have to rely on expensive nursery) that factored in for us. Good luck, it was a long head battering rd for me to reach a decision!
) I don't think you'd ever regret another child. But I worry. 
