My 4.5 y/o female shollie keeps getting different sized lumps & bumps, mostly on her flanks & back
It is impossible to say what is causing this without a proper physical exam, so visiting a veterinarian to confirm would be the best way to treat this. Bumps can be a number of things, it is common for red bumps that are very small to be a symptom of allergies, especially if there is itchiness associated with it. Here is an article about allergies if you would like more information: https://www.vetbabble.com/dogs/health-dogs/dog-allergies/
It is also worth mentioning that this could be a sign of fleas as flea bites could also cause these sorts of symptoms. It is important that dogs get appropriate flea treatment, even if you don’t see any fleas: https://www.vetbabble.com/dogs/health-dogs/dog-cat-may-fleas-even-never-see/