I really don't think I can give myself an overall number. For one, as others have mentioned, it changes with my mood. In addition, my insecurities now almost always have to do with how I "fit" in the world or with other people. I often feel like I have certain strengths and capabilities, but I can't use them for anything, can't positively influence anything around me or make anything happen. Can't say.
Perhaps 2 or 3? I don't know. It takes certain situations to coax it out of me because I tend to be very good at repression and dissemblance, and I don't like too much introspection naval-gazing. It's just too boring and circular a process.
I don't think anybody is entirely free of insecurity, though, even if it's not of the deep, lifelong pathology-inducing sort.
I tend to not think about my insecurities, i.e. I block them out. Even in the days when I was "more insecure", I would block them out. This probably means I'm out of touch with my insecurities, but I'm fine with that; the alternative is thinking about them all the time, which is something I refuse to do.
On a normal day, I'm at 0. On days when the insecurities nag at the back of my mind and I have to force them out -- with no hint to the outside world of what's going on in my mind -- I'm at a 3. When I have massive INFP shadow moments (i.e. "under extreme stress", as the typology trope goes), I'm at a 10.
There's literally no middle ground between 3 and 10.