Prince visited a pharmacy four times this week.
The 'Purple Rain' singer - who was found dead at his Paisley Park compound in Minnesota this morning (21.04.16) - made his last visit to a local Walgreens at around 7pm last night (20.04.16), and insiders told TMZ staff were concerned because the iconic star looked "much more frail and nervous" than usual.
On April 14, Prince was taken to hospital with flu after his private jet made an emergency landing, but left the medical facility in Moline, Illinois after just a few hours.
And a source at the hospital admitted to the website that they felt the singer left too soon because he was "not doing well" and needed further medical care.
However, the day after leaving hospital, Prince attended a $10 dance party near his home in order to give fans "living proof" he was OK.
Though he didn't perform, he told the crowd: "Wait a few days before you waste any prayers."
A cause of death has not yet been disclosed.
Prince's publicist confirmed the news of his death in a statement earlier today which read: "It is with profound sadness that I am confirming that the legendary, iconic performer, Prince Rogers Nelson, has died at his Paisley Park residence this morning at the age of 57. There are no further details as to the cause of death at this time."