Need advice - ultrasound didn't find lump, but the GP and I felt it. What do I do now?

Hi there, I have a lump around my collarbone area on the left. It’s been there for a few months, I’ve noticed it getting a bit bigger. I went to the gp and his response was “don’t worry it’s just tissue!” And ordered no tests what so ever. My family has a big breast cancer history with my mother dying from it. So I took it upon myself to go private for an ultrasound and here’s where it gets strange. They say “we can’t find any lump” but then it’s literally there and the gp felt it too. So I am confused, because there definitely is a lump and now I’m like do I go back to the doctor or do I just leave it?