One view findings - going back for more images

Hello

I've been getting mammograms every year since I was 40. I was called back on my first (ultrasound plus mri) and it all turned out well. Got called back for the same spot a year later and was investigated again and it was well. I started HRT when I was 42 due to premature menopause and my gyno wants to keep me on it until I'm 50. I'm 45 now and have once again received a call back for the same breast I've been called back on before. This time they said there was an area of density on one view that wasn't on the other - I actually saw the 2 images when they did the mammogram and it was plain as day to me so I was expecting a call. My dr said its most likely overlapping tissue or a fold. Is this pretty common - anything to be overly concerned about. I have health anxiety and its been pretty bad in the past (I didn't get out of bed for 2 days before my mri - I was terrified). I'm in a better place now but still concerned. Thanks!