Rep. Hill -- a Democrat --  issued a letter Sunday, saying she was stepping down from her elected post in the House of Representatives after winning the seat in last year's election. She repped California's 25th congressional district, covering parts of Northern Los Angeles.

In the document, she makes some damning allegations against her estranged husband, Kenny Heslep ... whom she's in the middle of divorcing right now, and it just got nastier.

Hill writes, "This is what needs to happen so that the good people who supported me will no longer be subjected to the pain inflicted by my abusive husband and the brutality of hateful political operatives who seem to happily provide a platform to a monster who is driving a smear campaign built around cyber exploitation."

She goes on to say, "Having private photos of personal moments weaponized against me has been an appalling invasion of my privacy. It's also illegal, and we are currently pursuing all of our available legal options." The implication is that Heslep facilitated the leak.

If you hadn't heard ... nude photos of Hill surfaced last week, as did news of extramarital relationships she allegedly had with 2 different people -- a congressional staffer of hers, and a former campaign aide. She admitted to the aide fling, but denied a staffer affair.

Hill finishes her letter by saying that she's stepping down to avoid further pain and embarrassment being thrust onto her and others, while also apologizing for her mistakes.

She writes, "Thank you for allowing me to turn my focus on this particular battle right now, and know that I stand with you as we continue to fight for the many important issues that brought me to Congress in the first place."