I have a well lost pressure then after awhile its back has done this a day. Checked that there are no toilets running etc. Pressure in holding tanks is good.Any suggestions.

When you have no water, does your pressure tank show pressure on the gauge?

Yes I wonder I have a filter unit under my crawl space if the filter needs replaced could this be the cause

Could be. But the filter unit would tend to be a problem ALL of the time or NONE of the time. Still, it probably has a bypass. Turn the bypass and see if that solves the problem.