Audience members, some of whom were also weeping, assisted by singing along.
People magazine reported the singer told fans she was feeling hormonal and had been suffering from cramps.
Drying her eyes, she said, "I told you I was a mess." Lambert and Shelton were married 2011-15.
In 2001, he made his debut with the single "Austin".
The lead-off single from his self-titled debut album, "Austin" spent five weeks at number one on the Billboard Hot Country Songs chart.
The gold-certified debut album also produced two more top 20 entries ("All Over Me" and "Ol' Red").
PHOTOS: 2016 Academy of Country Music Awards Red Carpet Arrivals The couple posed holding hands together outside the event, and a source backstage said the couple was being very affectionate.
Also, we have to mention that Miranda absolutely slayed on the carpet in a yellow silk radial pleated Christian Siriano gown and stunning pink satin Joyce Echols heels with a mini gun and holster design on the side.
Many had been speculating about whether Lambert's ex, Blake Shelton, might bring girlfriend Gwen Stefani to the show as well, however, the two did not walk the red carpet together.
Lambert and Shelton split in July after four years of marriage, and have remained relatively amicable and supportive of one another since ending things.
"Marriage is a tough business, and we gave it our best college try," Lambert told co-judge -- who also called it quits with her ex, Gavin Rossdale, last August after 13 years together -- have become increasingly public in their affection for one another since rumors began to fly about their romance last October.
Meanwhile, Miranda has moved on with Anderson, posting sweet snap on Instagram in January, and on Valentine's Day, the couple performed a Mariah Carey duet together in Northampton, Massachusetts.