Michelle MCNamara passed away in her sleep and now the Young Adult star has opened up about what may have caused his partner's death.

He tells The New York Times his wife had been working long hours in the weeks leading up to her passing and took some Xanax pills to help her sleep - but never woke up.

"I have a feeling it might have been an overdose," he tells the publication. "That's what the paramedics there were saying while I was screaming and throwing up. I was literally blinking trying to get out of this."

Oswalt, who was left a single parent following his wife's death, also admits he turned to alcohol to help dull the pain.

"I found out the hard way these past few months that alcohol really doesn't help," he explains.

But his young daughter and his comedy have been a constant source of comfort in the wake of the tragedy.

"I'll never be at 100 per cent again, but that won't stop me from living this," he says.