poisenverte,
Low pressure due to a low refrigerant charge is a common cause of the clutch engaging and disengaging repeatedly.
To rule out a clutch gap, or a clutch coil problem, you can use a jumperwire at the low pressure switch connector. Unpug the low pressure switch and jumper the connection. If the clutch stays engaged, then you know that the problem is "low pressure".
If you lost refrigerant you have a leak, period. If you lost refrigerant you also lost some of the oil. If you are going to just add refrigerant, you should also add a couple of ounces of oil. One to two ounces should do it.
Too much oil can have a detrimental affect on the systems operations, so don't get carried away with the oil! rangerj