Es ist mir egal, was du von mir hältst.

This would be the most natural way.

Es ist mir egal, was du über mich denkst /

Es ist mir egal, was du von mir denkst.

Those two are okay as well.

(Or let's rather say I think they are higher in style.)

wie sagt Man ...

Try this: Es ist mir egal, worüber du an mich denkst.

Actually, I see a problem here with a double use of prepositions.  It can be: denken an or denken über.  In this construction since both prepositions take the accusative, it would seem that one would choose one or the other of the prepositions, thereby disqualifying my so-called correction above.  However, technically, an can also govern the dative.  Why not say: Es is mir egal, worüber du an mir denkst.  This would place the preposition an in a secondary roll in its relationship with denken.  Really, I am only guessing.  I have not been with German at all for years.  I can look further into it, but a native speaker could know perhaps with some ease.  That is the awesome leverage that italki gives.  Thanks for being so polite, but there is no need to stand on courtesy.  Sorry for this confusion.  However, may I please say I think there is no strong case for an mir since denken is so strongly associated with denken an plus accusative.  Your sentence is probably very good.  How about:  Es ist mir egal, worüber du über mich denkst.  That must be correct also,  and just saying mich without  a second preposition does not come across as ambivalent.  I should have put my take on this under comment, not correction!!  However, it was too interesting to turn down.