sounds like we've had quite similar experiences - I went home after one night in hospital with dressings on both boobs and one under right armpit (lymph node biopsy) and no-one to help with washing etc. The dressings stayed put until I went back for my first follow up appointment (about a week after the op) when the full ones got taken off and lighter one put on the right side (mastectomy side). In terms of keeping clean I used unscented baby wipes as much as I could around dressings and roll on deoderant (aloe vera based from health shop so hopefully no nasty chemicals) on 'good' armpit. When first lot of dressings were taken off everything had healed well and scar in armpit looked 'clean' with no sign of infection.
Do you know when you are going for follow up appointment for dressings? x