To know about yours sperm count : you have to do semen analysis report. For that, you to remain abstinent from masturbation for a week and than give seminal sample in reliable pathology laboratory. They will analyse your semen by preparing slides and see under microscope and give report about sperm count and its motility.
Next Steps
You can do masturbation as per your natural rhythm of sexual desires. No any fixed frequency has been recommended. Masturbation does not cause back pain commonly.
Health Tips
For proper sex education and healthy sexual life, kindly consult me online during evening time. Happy to help. Take care.!!