Pathological liar or real story?

A guy I've been dating for a few years told me early on that a former girlfriend, whom he wanted to marry, had died in a car accident on her way to see him one night back in 2012. He told me he felt guilty for what had happened and tried to kill himself twice with a handgun he owned. The gun misfired both tines, and he decided to keep living. I've asked several questions about her, her family, and their past together. Apparently, her sister committed suicide in 2015. He says he has been unable to reach her parents since then. I encouraged him to go to counseling to help deal with everything. One day, I decided to google the former girlfriend. I was unable to find anything about her online- not even an obituary. I asked again for the names of her parents and searched them, along with her sister. Again, I found nothing. There are also no social media accounts for any of them. I suggested visiting her grave site, writing her a letter, and reading it to her to help with the trauma. He told me she was never buried, and neither was her sister. He has lied to me before when I confronted him about his porn addiction. He denied it even though I showed him screenshots of what I had seen. I know he is willing to lie to avoid feeling embarrassed, and probably for other reasons as well. My question is: Is he lying about this former girlfriend? About killing himself? About her sister and their family? I'm happy to provide more details. Please help.