Yes. I often have golf ball sized clots (and sometimes larger) coming out. There is no need to panic, at least that is what it seems like you have been doing. My periods are far from normal. You're not going to die from it, many women bleed much more than that for longer periods of time and as long as they watch their diet and take it easy, they're fine (well, as fine as someone can be with that condition.)
I hope it gets taken care of and you find the source, but you really shouldn't be so panicked.