I found a large lump in my breast that is getting bigger...?

A few months ago I noticed a rather large lump near the top of my right breast. I have recently lost about 50 lbs and thought maybe the change in shape could just be from weight loss. I also considered that since I had been working out that maybe it was just muscle that had developed. The lump has seemed to grow in size and is now a little bigger than a golf ball. At times it is tender to the touch and feels much different than my left breast. I know I should go to the Dr but I currently don't have insurance. I start a new job with medical benefits in a couple of months and was hoping to put off a Dr's visit until then. My main concern is going in.. finding out I have cancer... and then not being able to get coverage because of being labeled "previous condition" I really don't want to worry my family or friends so I haven't really mentioned it to anyone. I want to be sure before I put them through any of that. I'm afraid of waiting to long to go but more afraid of being a burden to my family.