After serving a two-year doping ban, Jack has secured swims at this year's world titles and the Commonwealth Games.

Jack finished second in the 100 metres freestyle final at the national championships in Adelaide on Wednesday night.

That achievement secures selection for the worlds in June and the Commonwealth Games in July-August.

Jack says few people know the extent of her despair when suspended for testing positive to the banned substance Ligandrol about three weeks prior to the 2019 world titles.

"Not many people really know what I actually went through, the depths of it," she said.

"To be back and wearing those (Australian) colours again means more than anything to me.

"I can't thank (enough) all the people in my inner circle who got me through and got me back to swimming.

"My goal was to ... fall back in love with swimming again and I have. I am really, really proud to be back."

Initially banned for four years, Jack's suspension was reduced on appeal to two years when the Court of Arbitration for Sport found Jack did not knowingly ingest the substance.

The 23-year-old admitted fearing she would never return to an Australian swim team.

"There was a lot of times I thought I might not get to this point," she said.

"And not just because of the whole (doping) case.

"I struggled. I lost touch with why I love swimming and why I did swim."

Coach Dean Boxall and sports psychologists were crucial in rekindling her desire to swim.

"Dean was patient with me, he reminded me of all those things that I loved," Jack said.

"I just worked harder each day ... and it's still a journey.

"I am still learning and doing things with psychologists ... and that has been really beneficial to my comeback.

"To be completely honest, I am stronger, I am fitter and faster which I just proved.

"This is just the beginning for me."

Australian Associated Press