Frightened - Mastitis Vs inflammatory cancer

Hello! I'm new here. I'm a 51 year old woman without much significant breast history except for fibrocystic/heterogeneously dense breast tissue. Birads 2. When I was younger I had frequent diagnositic mammos and USs because my breasts have always been lumpy. But, after I had my ovaries removed 14 years ago (endometriosis) and then stopped all oral hormone replacement 8 years ago, I've only required screening mammos despite the density of the tissue.

My mother did pass away from MBC (ductal?) but she refused all treatment and just hoped for the best.

I woke up yesterday and soon realized that I had a slightly uncomfortable pulling sensation in my left breast. I went to rub it and felt a pretty significant lump/thickening of around 1 cm. I immediately called the doctors' offices and set up an appointment for today. As the day progressed I noticed a small area of redness on the breast over the thickened part. Not a pimple, just reddened skin. By bedtime the redness had grown. And,this morning the lump is bigger (doctor measured it at 3 cm) and the skin is still red.

A doctor saw me today and prescribed antibiotics for possible abscess and also managed to get me an appointment at the breast clinic early tomorrow morning for a mammo and ultrasound.

I'm worrying myself to the point that I'm nauseous. I've never had a breast abscess and I cannot fathom how or why mastitis would occur in a woman my age. And, I'm not feverish and I've always heard that abscesses of the breast were painful. This mass is tender when pressed but otherwise is painless.

Anyone else ever face breast infection vs cancer diagnosis?