Apparently, you've never heard of the law of conservation of mass. It completely undermines your claim that mass has a beginning or and end. As far as we can observe, outside of some applications of general relativity in an expanding universe, mass is conserved even as it may change forms. Assuming that mass had a beginning would be assuming that the law of conservation of mass did not, at some previous point, exist. There is no evidence whatsoever for such an event. Arguments premised on made up "facts" are necessarily incorrect.
It means that for you the BB was a lie from the onset. I understand why since the father of the BB theory was a theist called George Lemaitre. What a fallacious attitude!
Mass is evidence of matter and matter is the composition of the universe. Since matter could not have caused itself to exist, the Primal Cause is on.