On a 5yr probation for caught with drugs... 1week ago I shoplift was just one item for $3.. will I have to do 5 yrs in prison?.

I don't think you will have to do five years in prison. That is pretty steep for a crime such as yours; but why did you compound your troubles? You will have to wait for your court date to see what will happen. You were on probation after all, and then committed another crime; doesn't matter for how much. Are you testing the system?
Tick

Most likely no, but, you have to report this right away. Not reporting it, is a much more serious violation than the shop lifting.

So it is a violation, could they send you to prison for 5 years, yes they can. If this was another drug charge, or a more seroius crime, I would expect they would make you serve at least some of the time.

So you report it to the PO, and see what happens. Most likely a stern warning.

On a 5yr probation for caught wih drugs ...1week ago I shoplift was just one item for $3 ..will I have to do 5 yrs in prison ?......

If you report this to your PO immediately, then you may or may not be violated. There may be a VOP hearing held on this as well. It all comes down to what the judge says and does at your VOP hearing. Take a look at your final sentencing paperwork to see what jail time could be imposed on you for violating your probation and go from there.