Unlikely. Leukemia's a pretty quickly-progressing disease, so if you noticed a petachiae rash in February, and you're not more sick by now, chances are it's nothing. Especially not if you had clean bloodwork in January.
I doubt petachiae would be your only symptom if you had leukemia. Do you feel like death warmed over? I went through this scare a few years ago, too. Do you have just a few dots or does your entire leg look red?