Scheduled for diagnostic mammogram of one of my breasts, and a possible sonogram, should i be worried?

It's normal to worry: Many women get called back after their screening mammogram. The diagnostic mammogram and ultrasound is only a way to evaluate more closely and area of possible concern that the radiologist might have. For some women it might end here, for others a biopsy might be recommended. Still it means nothing until the biopsy result is back. Based on that further recommendations will follow.

Not yet: Get the studies first. May be nothing. Doctors are being thorough.

It is normal: to be concerned or worried, because obviously there is a potential abnormality. However, most of these turn out to be nothing of concern, so keep that in mind.