We talked to Bristol for a new documentary airing Monday at 9 PM ET/8 Central on FOX -- delving into the horrors of famous people who've had to battle obsessed fans ... to the point their lives have been put at risk, including BP here -- whose history with this is well-documented.

The incidents for Bristol date back to the mid-2010s ... and they were all harrowing.

In the years since, Bristol hasn't shied away from the fact that she exercises her 2nd Amendment right to bear arms -- something she touches on here in our sit-down with her.

Check it out ... she describes the anxiety she lives with in the aftermath of everything she's gone through -- and explains why she feels protecting herself, her home and her family is absolutely essential in her daily life going forward.

Part of the reason she feels she needs to go to these extremes is because the law itself is simply too lenient when it comes to stalking -- and doesn't do enough to deter them.

We get far more into the topic in the doc itself -- titled 'TMZ Investigates: Obsessed and Dangerous: Hollywood’s Stalker Crisis' -- and cover more stars who've dealt with this.