If you're concerned about irregular density then it is very important to talk with your doctor. As, Masses with irregular shapes and indistinct margins have a higher likelihood of malignancy( Malignant means that the tumor is made of cancer cells). But I hope that it will not be that serious.
I'll suggest you to consult with your doctor and get the diagnosis as soon asap before it gets worse.
Did they call you back? I had a 3 D mammogram due to dense breasts. Density means that they can't see as well as they like. Looks like area of grey blurriness on a mammogram. Normally it means they are going to want to take a second look.
The purpose of the initial screening mammogram is just to find anything that catches the radiologist's eyes. These might include a mass, asymmetry, architectural distortion, and/or grouped calcifications. For example, if there is a focal asymmetry, the patient is recalled for diagnostic mammogram with additional views. Most of the time, focal asymmetry presses out with spot compression views, suggesting normal superimposed fibroglandular tissue. If the abnormality persists with spot compression, the radiologist might recommend ultrasound +/- biopsy. Good luck!