You could, I guess, but you might be charting in vain, as you may be in for a long wait! I guess it will be tricky to attempt conception of a girl based on charting methods whilst still BF, as I think girl conceptions are usually before ovulation, & without a pattern to go by, you would still be making a stab in the dark.

However, you never know, your first ovulation may be just around the corner and by charting you may just catch it?

It might be worthwhile charting to get an idea of what your body is up to, but still take non-hormonal contracteption, until your chart showns you are ovulaing/you get AF back, then you know that you can clearly use charting for concieving a girl?

Good luck,