My period came only for a day instead of 4 days...

what is the explaination of medical condition you mentioned :

its more likely to get this effect by using the medication ( steronate ) which effect on productive system hormones which lead to change in uterus lining and change the period cycle 

what is the next step :

1. visit a GYN doctor to do the needed medical checks and make sure of productive system health 
2. stick to a healthy life style including : healthy food , exercise , have plenty of rest ) 
3. avoid anxiety and stress 
4. consult your doctor about the medication you are using and if there a need to change or stop it 

other possible causes :

1. life style 
2. stress 
3. hormonal changes 
4. productive system chronic diseases such as ovarian cyst 

needed medical examnations :

1. physical examnation by doctor 
2. blood and blood chemistry test
3. urine test 
4. physical examnation of productive system
5. ultrasound test for productive system