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I personally didn't find khan academy's physics videos very helpful or informative.
I used pic related when I self studied, and it was pretty good. I think the standard for college physics is University Physics by Young and Freedman. My school didn't offer AP physics courses, so I had to self study then take the exams on my own. Passed mechanics and e&m, both of which go further than a college physics I&II course.
The best thing was the 8.01x/8.02x lectures by Walter Lewin. You can find them on YouTube. I don't usually like lectures, but this guy makes physics very fun to learn.
Don't be afraid of starting with college physics. It doesn't assume you know anything, and teaches the basics in a rigorous way that allows you to learn further physics.
If you are trying to learn math/physics at a college level and gain a solid intuition, I find short khan academy videos aren't enough. I actually spent less time overall learning calculus when I watched Professor Leonard and knew how to do the problems vs watching Khan academy then struggling with them.
