Catelynn Lowell and Tyler Baltierra are proving that "happily ever after" doesn't just happen in fairy tales: The high school sweethearts are still engaged to be married and getting ready for what's sure to be a very special new year -- thanks to the upcoming arrival of their daughter in January.

But their road to happiness wasn't always a smooth one: When we first met the duo on "16 and Pregnant," they were struggling to prepare for their first child. Eventually, the teens wisely accepted the fact that they didn’t have the resources to raise a baby -- or the stable home environment that their offspring would need -- and made the difficult decision to devise an adoption plan for Carly.

Over the next five years, Cate and Ty's relationship was chronicled on "Teen Mom." We saw many highs -- and many lows -- but through it all, their deep love for one another persevered. So now, before Baby TyLnn arrives -- and “Teen Mom” makes its triumphant return to MTV -- we're taking a look back at the couple’s path to (almost wedded) bliss:

The biggest decision of their lives

Catelynn's first pregnancy was't easy: In between bickering with loved ones, she and Ty -- with help from their adoption counselor Dawn -- were busy searching for the perfect family for their baby girl. Through it all, the two became each other's invaluable support system, and after Carly was born, they made the brave judgement call to give her to Brandon and Teresa.

The future Mr. and Mrs. Baltierra

Ty couldn't hold back his tears when he asked for Catelynn's hand in marriage. "I want you to be mine forever -- I want you to grow old with me," he declared. She gleefully accepted his proposal, and they sealed the unforgettable moment with plenty of hugs and kisses.

Moving on out

Shortly after their engagement, Tyler had difficulty opening up about missing Carly and eventually began to pull away from his fiancée. Things got worse: Tyler and his mom soon requested that Catelynn leave their home and go back to her mom's house.

Trust issues

Catelynn revealed that she lied to Tyler about sleeping with her ex and texting her former flame. The reason: She said she didn't want to hurt her fiancé, but she soon learned the hard way that deceiving him would only cause him more pain. He ultimately forgave her -- but not without giving her some tough love that showed why her behavior was unacceptable.

An unforgettable afternoon

Catelynn and Tyler's reunion with their biological daughter was filled with joy, smiles and plenty of happy tears.

Overcoming insecurities

Cate began to experience body-image issues, and her self-doubt only intensified when Ty followed an urge to break away and hit the club scene without her. Luckily, the two didn't keep their feelings to themselves and emerged from the rough patch with a better understanding of each other. And best of all, they even hit the dance floor together!

Questioning their commitment

During the "Being Catelynn" special, the couple sorted through their latest issues -- including Tyler's decision to postpone their wedding indefinitely. Catelynn couldn't help but feel anxious about their uncertain future, but they ultimately reached a healthy resolution and remained committed to each other.