Bro,
I feel that sins prior to Islam are forgivable if the person sincerely repent, and all sins after Islam — except shirk — are equally forgivable for Allah's mercy is far greater than our sins.
Coming back to your peculiar question, it seems you are going through a test... the kind of test which you know very well, Steadfast and keep your dignity..
On a lighter note, what gives you the impression that born muslims commit those acts lesser than the revert ones. Only a handful people like you who have this level of Taqwa to stay away from those acts.
