WATCH: Heidi Montag Cries in Front of Her Mom’s Fake Grave

Heidi Montag is breaking down her problems.

In a preview clip for Lifetime’s The Mother/Daughter Experiment: Celebrity Edition provided exclusively to Celebuzz, the former The Hills star turns on the waterworks as she struggles to deal with her emotions on an upcoming episode. When confronted with the reality of her mother Darlene Egelhoff’s mortality after she’s presented with her tombstone, Montag bursts into tears and admits she hasn’t always been the greatest daughter ever since becoming famous.

“I’m so, so sorry. I feel like I hurt you the most of anyone in your life,” she says, sobbing. “I’m sorry. I didn’t mean to. I really didn’t.”

She continues as tears roll down her face, “I was just so self-involved and I had so much going on.”

Previously, Montag told us that finding fame at 19 caused a rift in her relationship with her mom.

“It was just a very challenging time for me and I think I felt emotionally responsible for the well-being of my entire family from a very young age,” Montag, now 29, said. “And I think that in order for me to be able to kinda survive and take care of myself I just had to cut my family off, which was not the right thing to do but it was all I could do at that time to … survive basically and be able to move forward in my life.”

“The Mother/Daughter Experiment: Celebrity Edition” airs Tuesday at 10/9c on Lifetime.