wondering

I am very thankful for my life, my husband, our son, our home, our church family, everything we have! So I wonder, why am I consumed with this desire/obsession over becoming a mommy again? I have so much here to keep me busy, so much to be thankful for. I shouldn't want more! But I can't just lay these thoughts aside - they will not go. Part of me feels that if Im truly thankful for everything I have, than I wouldn't want anymore. But, that's obviously not the case. I am ready for a little one! What's a girl to do?