Jason Troitsky, 37, was discovered unconscious at his home in Outwood Common Road, Biller-icay, with a black bag over his head on October 18 last year. The bag was full of helium gas, which was flowing from a linked canister.
He was taken to Basildon Hospital, where he died ten days later from respiratory failure.
The software developer, who was born in Zimbabwe, left a suicide note, an inquest heard on Friday.
Speaking after the hearing, at Chelsmford Coroner’s Court, his fiancee Anka Troitsky, 41, said Jason had referred to suicide as “plan B” after he was denied access to his five children from a previous marriage.
She said he was a “tortured soul” and would often find him crying in front of the bathroom mirror.
She said: “He would always say ‘I just want to be with my kids’.
“I could see him getting lower and lower. He became very depressed and ill. I used to have to read to him to help him sleep.”
The couple lost their own baby when Anka miscarried last year, but planned to start their own family and marry last Christmas.
Anka added: “He was doing well in his career and we had a future together.
“Now I am just trying to come to terms with what happened and I hope today will help.”
PC Sam Lewin, from Grays police station, told the hearing there were no suspicious circumstances surrounding the case.
Recording a verdict of suicide, coroner Caroline Beasley-Murray told Anka: “The court expresses its deepest sympathies to you.
“I hope you can treasure the happy memories you have of Jason.” ECO