Showing what appeared to be a positive pregnancy test to the camera, Carter announced, "Obviously I have a baby on the way. I'm going to be a busy father for sure."
"This is the official announcement, we're pregnant," he added.
The "I Want Candy" singer alluded to the baby news in an Instagram photo featuring himself posing shirtless in front of the mirror. "Dad bod," he captioned the selfie.
Earlier on Tuesday, Martin seemed to confirm the couple -- who first went Instagram official with their relationship back in January -- were back together as she shared a photo of the two kissing. "Love wins," she wrote in the caption.
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The news came almost a month after Carter said he was "#single" on March 30 -- one day after Martin was reportedly arrested for domestic violence following an alleged fight between the couple.
According to TMZ, the L.A. County Sheriff's Department went to Carter's home at 11 p.m. on March 29 for a domestic violence call. Martin was taken into custody and held on $50,000 bail. Carter later told the outlet Martin informed him she was pregnant right before they got into the argument. He also admitted that he didn't believe her and said there was "no chance" they would be getting back together.
Carter appeared to address the alleged altercation on Twitter, writing, "You don't have to wait for someone to treat you bad repeatedly. All it takes is once, and if they get away with it that once, if they know they can treat you like that, then it sets the pattern for the future."
While speaking with People, the "Aaron's Party" singer confirmed the couple had reconciled and all of the charges against Martin have been dropped.
"We just realized that we love each other," he said. "Family is most important to me."
Carter also spoke about his future with Martin and his thoughts on being a father.
"This is what we both want," he said of the baby news. "We both were trying for it. I'm just focused on the future and being a dad. I want to be a good dad. I'm focused, my music career has been doing really well, and touring, having my clothing line out, all that stuff I have going for me that isn't necessarily just music. Family is most important to me."