Re: sucking thumb
By 3 months, a lot of babies have discovered how to extract maximum milk in minimum time, so it's normal for nursing sessions to be shorter than when your LO was a newborn. Babies who discover that they enjoy thumb-sucking may choose to do their comfort sucking on their hands, rather than on mom. It's generally not a problem, because babies know that thumbs don't deliver milk and when they are hungry, they will swap thumb for breast.
If you're concerned, keep an eye on baby's diapers (good output = good input) and don't be afraid to offer the breast if baby hasn't nursed for a while.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"