On Wednesday, the New York State Athletic Commission denied Miller a boxing license, all but ending his hope of being able to challenge unified heavyweight world titlist Anthony Joshua on June 1 on DAZN at Madison Square Garden in New York.
But in a video posted on Instagram on Friday, the 30-year-old said he had made a mistake.
"I missed out on a big opportunity and I'm hurting inside".
Miller and Joshua were set to meet in NY on June 1 and Hearn says he has now learned of a second alleged doping violation by Miller, meaning that fight is now dead in the water.
Miller's adverse finding for GW1516, a metabolic modulator also known as cardarine and endurobol, was recorded on 20 March.
"A lot of ways to handle this situation, I handled it wrongly and I'm paying the price for it".
"My heart is bleeding right now, I hurt my family, my friends, my team, my supporters, but most importantly I'm going to own up to it, deal with it, and I'm going to come back better and I'm humbled by the experience".
On Friday, Rafael reported that subsequent drug tests revealed more banned substances in Miller's system.
Miller's participation in the Madison Square Garden bout was thrown into doubt on Tuesday when Vada informed both camps of an "adverse finding" in a drug-testing sample, leading to him being denied a licence for the fight.
The 20 March sample showed traces of a substance called GW1516, which is banned because it can improve aerobic power and endurance.
Promoter Eddie Hearn said he was scrambling to find an alternative opponent.
And Ortiz is Joshua's own preference, who he knows will be seen in the United States as a more unsafe opponent than Miller. "AJ's June 1 opponent will be announced next week - if you don't think you can beat him clean then delete my number!" he wrote on Twitter. "Fighters, we go through a lot and I don't want to make a bad name for ourselves and it's time to do right and get right".
Whyte, Miller and Fury have all been caught out for failed drugs tests, while AJ hasn't been found committing any serious wrongdoings in that area.
The Madison Square Garden fight was set to be Joshua's USA debut.