Justin Bieber's Marriage 'Threw' Selena Gomez 'Off Guard and Hit Her Hard,' Says Source

Justin Bieber‘s engagement and marriage to Hailey Baldwin came as a surprise to the world — but the developments have had a deeper impact on his former longtime girlfriend, Selena Gomez, a source tells PEOPLE.

“Selena can be a delicate flower, especially because she has had constant medical struggles, but Justin’s engagement and quick marriage threw her off guard and hit her hard,” a music source tells PEOPLE.

Gomez, 26, is seeking treatment after recently suffering an emotional breakdown while in the hospital, a source confirmed to PEOPLE on Wednesday.

“She and Justin have been on and off for years, although they were so young when it all began,” adds the insider. “Justin was her first big love, and she isn’t over him.”

The “Wolves” singer experienced “a panic attack” during her second hospital stay in just a few short weeks — she suffers from a low white blood cell count, a common side effect for kidney transplant patients — a source told PEOPLE.

Now the music insider says Gomez is on the mend as she seeks treatment and is eager to get back on track.

“Selena is feeling better,” the source says. “She is getting the help she needs.”

As for how Bieber, 24, has reacted to Gomez’s struggles, “It’s hard for him to hear that she isn’t doing well,” a source close to Bieber told PEOPLE after the Canadian pop star was spotted crying in a vehicle with Baldwin, 21, on Thursday following news of Gomez’s recent hospitalization. The pop star was also photographed that day hugging friends after driving himself to church in Los Angeles.

“This was his first great love, and while he was young and traveling around the world as a superstar, he learned a great deal from her,” a Miami music source told PEOPLE.

“He was extremely upset over what has happened to Selena,” the Miami music source added. “He feels like she is part of his life and he wants her to be happy and healthy.”

Discussing the impact of Gomez’s struggles on Bieber’s marriage to Baldwin, the music source said, “It could be a problem down the road.”

Still, the Bieber source maintains that his recent “gloomy mood” was not a direct result of Gomez’s challenges.

“Justin had a bit of a rough week, but was doing better over the weekend,” the Bieber source said. “He spent time with Hailey, close friends and mostly chilled. Like most people, he has his ups and downs. He felt a lot of pressure last week about things, like creating music, that he doesn’t feel he is ready for right now. For the past few days, he tried to just focus on things that makes him happy.”

The source adds, “Hailey makes him super happy. He feels bad that Selena isn’t doing well, but that has nothing to do with his gloomy mood a few days ago.”

RELATED VIDEO: Selena Gomez Seeking Treatment After Emotional Breakdown in Hospital Following ‘Tough’ Few Weeks

A source close to the “Back to You” singer previously told PEOPLE that Bieber’s recent marriage to Baldwin was one of many factors — both emotional and physical — contributing to her recent challenges.

“It’s been a combination of things affecting her emotional health,” the source told PEOPLE, referencing Gomez’s announcement that she would be taking a break from social media last month. “She has certain triggers and is also a very sensitive person which is why she cuts herself off from social media. The negativity and hate she gets affects her more deeply than most celebrities because she takes everything to heart.”

While the source added that “having Justin’s relationship everywhere isn’t easy,” Gomez has continued to grapple with health woes stemming from her battle with lupus and resultant kidney transplant in the spring of 2017.

“She’s also been dealing with other stressful situations and being back in the hospital was really difficult and brought back tough memories,” said the Gomez source. “It’s not fair to say this caused it or that caused it because depression and anxiety is so layered. She knows it’s something she will be facing for the rest of her life, but she’s committed to tackling her issues head-on.”