Swelling under left arm

I have had swelling under my left arm for a few months now. I figured it was due to breastfeeding but I'm no longer breastfeeding and the swelling is still there. I've also noticed a small moveable ball over my left collar bone and another on the left side of my neck. It's really starting to worry me. I've made an appointment for a breast exam next week but any input I could receive before my appointment would be greatly appreciated. I've already prepared myself for the worst diagnosis. :-(