As a new artist "you're supposed to start in a van and then you get a crappy bus and then you get an okay bus," Presley tells PEOPLE. But with the Annies, Presley and Monroe got to tag along on Lambert's luxury tour bus – at least most of the time.
"Sometimes if Miranda was headed in a different direction, Ashley and I would have to get on the crew bus back to Nashville and we'd be like, 'Ew! Crew bus! Boys!'" Presley says with a laugh. "Then Miranda would say, 'Shut up, both of you! I rode in a van for years with 10 boys farting and stinking. Y'all don't have a clue!'"
Now, as she gets ready to release her own solo album next month, "I'm starting to get a clue," says Presley. "In a very Miranda way, she prepared me for what I was in for and what I'm experiencing now. It's a lot more exhausting!"
Her album American Middle Class (out Oct. 14) will prove more revealing than anything she's done before, the singer shares. "My songs are so personal – they are like pages out of my diary," says Presley, 38. "They get a little bit embarrassing sometimes."
Take "Knocked Up," a song that is "as true as it can possibly get." The tale of unexpected pregnancy "came about when I woke up pregnant by someone I only knew for three months," she says. "I was freaked out. I'm from a one-traffic-light town in the mountains in Kentucky and I felt like I was bringing shame on my family."
In real life, Presley did not, as her song says, "ruin my family name," but instead had a son, Jed, now 7, and developed a good co-parent relationship with his father. "It's crazy because it is a such a wonderful blessing to have a child," she says. "It's a gift from God and to feel like it's going to bring shame doesn't make sense."
Jed has heard the song and loves it. But, she says, "He doesn't really get it yet. I'm not really looking forward to that conversation! But he does know that Mommy and Daddy just fell in love so hard that we did it backwards."
Listen to Presley's new single, "Knocked Up," here: