Bethany, you might find a dirt/gravel road with some hills and practice braking there, feathering the brakes and taking it easy on the front brake, which has more stopping power. Try keeping one finger on your brakes and as others say, and shift your weight back on the downhills. Practice braking just up to but not the point where your front wheel locks. Having you front wheel lock up can flip you off in no time. You had mentioned before having a few near misses and not being totatally comfortable on the 29'er. I think stepping back to working on skills on easy trails and dirt roads can help.

I am not a mountain bike rider. Yet. But I did ride motorcycle dirt bikes for some years.

But take lots of time to heal first!