The 31-year-old was initially expected to be back for the start of the new campaign but suffered a setback in July when he was admitted to hospital with a groin infection.
The talismanic midfielder finally made his first start for the Reds since March on Saturday and scored the opening goal in the 1-1 draw with Manchester United at Anfield.
But Gerrard admitted the lengthy spell on the sidelines brought some of the lowest moments of his career as he pondered his future.
“It’s only natural that you have doubts,” Gerrard told the club’s official magazine. “Different things cross your mind from time to time.
“When I got the injury I knew it was going to be a serious one, something that I wasn’t used to. I’ll admit that I was down, as low as I’ve ever been as a footballer.
“Before the operation I’d been getting niggles and having injections to play. I knew I wasn’t right. I was trying to put my body on the line. But it wasn’t the real me and I wasn’t the player I want to be.
“I was missing training sessions and coming in the day before a game trying to get that last session in, or having injections to play the next day.
“You can only do that for a certain amount of time before your body gives in, and my groin packed in on me.
“When it happened I was down and it took time before I got back in to a positive frame of mind. It probably wasn’t until a couple of weeks after the operation, when I got off the crutches, that I started being really positive again.
“Without a doubt the last six months have been the hardest of my career.”
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news