Seems like your boys are between the ages of baby - age 7. While those are busy years they're still the years where the kids think their parents have all the answers, they still admire and respect everything their paretns know and everything they do (except the discipline and saying "no" part). In a few years your older one will become a pre-teen and then the attitude begins. It happens with the best of kids - the kids who are wonderful helps, respectful and sweet. The teen years are really difficult - they're really rewarding - but emotionally they are really, really tough. The kids go through all of this self-doubt, they want to be nothing like you and your husband, and everything like the kids at school that they like. Bascially - they reject you as they try to extalbish themselves as their own person. It's not personal - it's what they do as they try to establish their own being. Most days are fine - and there are days when you are so proud and pleased of the good decision they made, or how mature they acted - but there are days that just tear your heart out. When they're young they come home to you to have you help them feel better when the've been hurt. When they're teens they go to their peers instead and you have very little idea of what's causing them pain. It can be that a friend dissed them in front of other kids, of that someone said something mean, etc. You can't fix it for them any more and they don't want you to - they want to deal with it on their own. Again, it's what they're supposed to be doing - but it's tough.
SOOOOO - when you have the yearning for another baby think forward to those teen years and remind yourself that as it is you'll "only" have to go through it with 3 boys... Once you get there you'll know what I mean. (And don't believe the adage that boys are easier than girls - they are different - different things hurt them, they respond differently - but getting boys through the teen years has it's own challenges...!