Confused? Should I go to clinic

Hi there very confused and worried.
Bit of history when I was 45 I have a very large immobile cyst which was drained. 2 years later, in the same place I have a lump which causes occasional pain and after period shrinks down. I went to docs when on period and lump was there well now, after about 5 days it shrinks down again and almost disappears. It done this last month. Will I waste breast clinic time for going with no lump? I say no lump it does however feel different there almost like a flat lump? Not it’s deep and not near surface anymore. It’s also tender to touch. Any advise. Obviously scared it’s cancer and the flat lump is thickening. Thanks

Also need to note. Gp felt and sis she thinks it’s good it shrinks and is sending me to clinic to get it checked and to have it aspriarted (again) but he hasn’t felt it when it has shrunk. Now I think ok maybe it’s a cyst but the flat lump afterwards is thickening. Not really sure if it is thickening. Confused.