My printer keeps losing it bed level settings

I have had this problem lots of times now. one day will have the printer bed settings in just right and then the next day i come and turn it on and the thing is 5 cm high and unlevel. I will re do it then after a few days it will go bad to some random setting. I have no idea why it is doing this andi can deal with it.

Give us more detail, something like Firmware you using a least.

I am using repetier for the firmware/

Make sure EEPROM is enabled

Proper sequence for Repetier:

Center effector:
G131 \\removes any offsets
M322 \\clears any bed measurements
G33 R0 \\clears any bed height maps

Center the effector (same exact height on all carriages)
G132 S1 \\measures endstop offets and stores in EEPROM
G28 \\Home printer

Run Autolevel:
G32 S2 \\measures autolevel and stores in EEPROM
G28 \\home printer

Run Z distortion correction:
G0 Z5 \\Run effector down to 5mm above plate
G33 \\Run height map measurements (will auto store to EEPROM)
G28 \\Home printer


Done.

I am not an advocate of auto level. Once you spend the time to learn to manually level a delta; all other times(if you need to) go very quickly.
be sure everything is mechanically sound and you leveling will be perfect. I have only had to relevel when changing nozzles or trying a new hotend.
Never had to autolevel and have made hundreds of parts.