Hayden Panettiere said her inability to tell ex Milo Ventimiglia “I love you” was a major “point of contention” in their relationship.

The actress reflected on dating her “Heroes” co-star when she was 18, and he was 29, in a new interview with US Weekly while promoting her upcoming memoir, “This Is Me: A Reckoning,” out May 12.

“Every relationship I’ve ever been in, I invested my whole self in,” Panettiere told the outlet. “I saw him as my partner and that it was going to hopefully keep going and evolving and lead to marriage.”

The “Nashville” actress said she “was unable” to say “I love you” to Ventimiglia, which made her “feel so uncomfortable.”

“I could only say ‘I love you’ in a casual way,” Panettiere explained, noting that since Ventimiglia was “older,” he was “more aware” of what those words mean.

“And that said a lot,” she added.

Panettiere, 36, and Ventimiglia, 48, dated from 2007 to 2009 after meeting on the set of the NBC superhero series.

Before their final split, Ventimiglia briefly broke up with Panettiere and then took her back, which she believes was because of her heavy emotions.

“One hundred percent it was only because I was over the toilet, hysterically crying,” she told the outlet.

The “Scream IV” actress said her “world had crumbled” when the pair initially split, which she felt “was so out of left field.”

“Nothing that big or explosive had happened,” she explained. “Nothing had really gone wrong. Nobody cheated.”

Panettiere recalled the “This Is Us” actor was in “pure shock at how visceral and massive my negative reaction was, and he immediately took it back.”

Page Six has reached out to Ventimiglia’s rep for comment.

Ventimiglia, who is now married to model Jarah Mariano, with whom he shares 1-year-old daughter Ke’ala Coral, has not spoken about dating Panettiere since 2017, when he said he’d “never do it again.”

“There are things that happen to you in your life that shape who you are,” he told Mr. Porter at the time, per E! News. “Everything I’ve been through from jobs to friendships to partnerships, everything has built me to who I am. You learn from it. You learn a better way of doing things.”

But Ventimiglia admitted he “wouldn’t change a thing” about the pair’s relationship because it gave him “perspective.”

After splitting from Ventimiglia, Panettiere dated Ukrainian boxer Wladimir Klitschko on-and-off from 2009 to 2018, during which they welcomed daughter Kaya, 11.

The “Remember the Titans” actress also got into a volatile, allegedly abusive romance with Brian Hickerson that lasted from 2018 to 2022.

In the US Weekly interview, Panettiere said it was “traumatic” and “brutal” to revisit her experience with domestic violence in her book.

She also came out as bisexual, discussed her brother Jansen’s tragic death and her addiction struggles, and more in the interview.