Tori Roloff was feeling full of purpose on Monday when she posted a new photo with her new son. The first-time mom gushed about baby Jackson on Instagram after welcoming the infant with husband and "Little People, Big World" star Zach Roloff last week. "My heart is so unbearably full. I've only spent 4 days with this little guy and I have fallen In love completely with him," Tori captioned a picture of herself kissing the newborn. "This is what I was meant to do," she declared. "Mommy loves you, Jackson! #BabyJK #zandtpartyofthree." Tori and Zach announced Sunday on Mother's Day that Tori gave birth to a son May 12. Zach said in a statement on the TLC website that mom and baby are "doing great." "Jackson has already mastered holding daddy's fingers and snuggling with mom! He is adorable and Tori and I are loving being parents," the 27-year-old reality star added. "Little People, Big World" follows Zach and his family as they live and work on their farm in Oregon. Zach and his parents, Matt and Amy Roloff, all have dwarfism and stand under 4'3" tall, while Zach's three siblings are of average height. "What a wonderful Mothers Day like no other. My baby (Zach) and his wife just had their first baby," Amy wrote Sunday on Facebook. "I'm so proud so happy I can't contain myself. I love them! My grandson is perfectly perfect!"