By Alexis Tereszcuk - Breaking Celebrity News Senior Reporter

Did Jesse James cheat on Kat Von D, causing their most recent breakup?

Sandra Bullock’s ex-husband is no stranger to stepping out on a relationship – she divorced him after his numerous affairs surfaced shortly after she won an Oscar in 2010. 

Bouncing back, he started dating reality star and tattoo artist Kat Von D, proposing to her, calling off the engagement, getting back to together again and then splitting again!

A woman who claims to have been hooking up with James while he and Kat were broken up and then back on says she was dating him while he and Kat were “on a break,” and posted a rant about him on the website www.cheaterville.com.

“You can't stay faithful because you hate yourself, therefore you secretly hate everyone else in your life. That's why you treat women like sh*t. Why don't you finally be a man and tell everyone why Kat dumped you this time?” The “scorned woman writes. “Is it because you lied to her and said that you didn't see anyone while you two were ‘on a break.’ How did she find out about me Jesse? I know you didn't tell her, and I didn't say anything because I didn't even know that you two got back together until the entire world found out.