I had my fourth a year and a half ago. Before I had all of them, I wanted them- like this undying (yet some days I'd think of it more than others) feeling of "I REALLY WANT ANOTHER!" Sure enough, we had her.
Unlike all the other girls, With her I almost IMMEDIATELY had a feeling of completeness. Like, "my family is all here". I also had this ecstatic feeling I had never experienced. I posted about it right after I had her on mamasource... I just had to tell everyone how wonderful I felt... and it wasn't just that I had HER, it was that I had ALL of us. Kinda weird and cheesy, I know. But my point is I KNEW, and I still know. Although she is much younger than your third, I don't think I will ever want more. My husband was sure as well, and since has had a vasectomy.
I know that there's a super-tiny chance of getting pregnant again, and hey, that would be okay with me if we did have one more. But, I don't ever want to try for another. We feel right and complete. The urge has vanished.
I understand what you are feeling, and I'm not saying to directly have another child... but as a person who had this feeling with all of her kids, I'll tell you that it does eventually go away... but for me it required one more:) And we are so proud and happy to have her! She's a delight and the very MOST different personality-wise and looks very different as well. We just love her, and also I'll say that having four is easier than three (for me).
Good Luck!
Okay... so below is the post I sent out right after I had my fourth child (so you can get what I mean)...
I just had my fourth baby on the 11th of this month... I have always gone "nuts" over the new babies and have ALWAYS loved being a M., etc... But this time it is different. I'm not quite sure how to accurately describe it but I'll try my best.
After having this darling baby I have been in SOOOO much bliss! I just feel so complete as a family now and as a person myself. There's this wonderful sense of accomplishment as if this IS my main purpose in life, and it has been completed. There's just also a tremendous feeling of relief like "finally we are all here together and now we can do this with the whole family- conquer anything!" I'm extremely happy. I also feel way more confident in my role as a mother. I'm seriously in a M. high:) Just being with my four daughters and husband together creates this awesome "force".
I never expected such a profound feeling as this to happen. I knew of course I'd be super happy to meet the newest one, but this just goes beyond that. I'm such a proud M. and also so proud to be a part of my family. I'll also mention that this is the first time I've been certain that I don't want anymore kids.
I just wanted to share this with all of you moms to just spread the love. I'd also LOVE to hear similar feelings from other moms or also those that strive for certain emotional and psychological connections. It is like no other...