The singer became engaged to pastor Chad Johnson in April, but Michelle reveals she chose to end it just a few weeks after he popped the question.
The couple subsequently worked to repair its relationship, but the bride-to-be tried to break up with Johnson again hours before she checked into a hospital for treatment, and days before she admitted herself into a mental health facility in July.
"I thought I was over depression," she tells People magazine. "I thought, 'I'm good! I've got love, I'm working out,' but I was so angry. The rage built up in me. I did not attempt suicide, but I was questioning (life)."
Williams has been dealing with depression since she was a teenager and it only got worse after she found fame with Destiny's Child.
"The entire year we were rehearsing every day for hours," she says of their grueling schedule. "I was burying it, and before you knew it, I was looking up out of the pit like, 'Oh my God'."
The 38 year old's mental health started to worsen once more after she reunited with her former bandmates Beyonce Knowles and Kelly Rowland at the Coachella music festival in April, and as she prepared to seek help, she tried to end her relationship with Johnson, only for him to brush off her attempts.
"I'd been there before in that darkness," Michelle explains. "I was like, 'No, you better go (to the hospital).' By the time I got there, I was stable."
"(However), I would've understood (if he left)," she adds. "He's been praying for a wife. He didn't pray for a depressed wife."
Williams and Johnson managed to put their relationship woes behind them and focus their efforts on Michelle's healing.
The couple is still undergoing individual therapy sessions as well as marriage counseling, and its journey to the alter will be chronicled on upcoming reality show "Chad Loves Michelle", which debuts next month.
"People fall off the fitness wagon, people fall of the wellness wagon, but I can't fall off the (therapy) wagon," she adds. "I have to get healed to live this happy life."
"It's not just about marrying Chad," she continues. "I finally found someone to do life with."