Story highlights John Welden pleaded guilty Monday

He was accused of tricking his girlfriend into taking an abortion pill

Welden faced a life sentence but took a plea deal

He is scheduled to be sentenced in December

Remee Lee was elated when she became pregnant, but those feelings quickly turned into a nightmare that won't let go of her.

Her boyfriend wasn't happy about the pregnancy, but it was Lee's dream to have a child. Until her boyfriend, John Andrew Welden, took that dream away.

This week, Welden, 28, pleaded guilty to killing their unborn baby. How? He tricked Lee into taking an abortion pill, causing her to miscarry.

"Every day is a nightmare for me ever since this began," Lee told Chris Cuomo on CNN's 'New Day' Tuesday. "Even hearing the guilty (plea) yesterday, it's hard to believe it, it's hard to read it and know that this actually happened to me."

Guilty plea can't take away pain

Lee, 26, was in the Florida courtroom Monday, dabbing away tears as her former boyfriend accepted a plea deal that could send him to prison for at least 13 years.

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Welden was indicted under the rarely used federal Unborn Victims of Violence Act, a murder charge that carries a life sentence.

Todd Foster, Welden's defense attorney, told reporters that the stakes of going to trial were too high.

"The possibility of a mandatory life sentence, no discretion to the judge, obviously is a big factor," Foster said. "Obviously it's tragic all around from every angle, and I think that's recognized."

Those who know Lee say she's still burdened by sadness.

"Nothing is going to bring back what was taken from her," Lee's attorney Gil Sanchez said.

She trusted him

Lee has said she was madly in love with Welden when she suspected she was pregnant.

They went together for a sonogram at Welden's father's Tampa-area clinic. The test showed she was six weeks pregnant. Despite her boyfriend's reluctance, Lee planned to have the baby.

Days later, Welden told Lee that her blood tests had shown that she had an infection and needed to take amoxicillin.

But instead of the antibiotic, Welden brought her Cytotec, a drug that causes contractions.

Welden told her to take three pills a day. She trusted him.

After she took only one pill, Lee was rushed to the hospital with abdominal pain and bleeding.

She lost the baby.

When doctors inspected the pills, it was discovered that they were not antibiotics, but abortion pills.

"There's just no words for the horror I wake up with every day that this is my reality. There's no escaping it, there's no turning it off," Lee said.

Welden said nothing as he left the courtroom Monday. Surrounded by security, he silently walked by a group of reporters, got into a black Hummer and was driven away.

Welden is scheduled to be sentenced December 5.