How long after all clear should you be concerned?

I had a thorough breast check, biopsy and mammogram 8 months ago after getting an extremely painful left Breast with a large solid lump almost overnight. (The mammogram was delayed by 3 weeks because of the pain and swelling). I was clear and told I have very lumpy breasts and sometimes you just get unexplained pain or swelling.

My mum has had breast Cancer twice and my sister has just been given the all clear after treatment.
I’m 48 and probably starting menopause soon so I’m very cautious.

4 weeks ago I had surgery for a stomach problem and after a few days I was aware of a large ‘triangular’ lump almost half the size of my breast. I’ve lost a stone in weight since my operation (to be expected). There’s no pain to touch it but the opposite side of my breast looks like it’s sunken. I can fit 3 fingers into the dent and If I press it, the flesh stays flattened and I even leave an imprint of my fingers. It can take about 10 seconds to plump up again.

I don’t want to waste my doctors time or get myself in a flap if this something to be expected with lumpy breasts so I just wondered if I should be concerned? If something were to develop would it have been picked up 8 months ago or can a problem occur since that time please?