Hello,
First thing you need to know is masturbation is completely normal. Men masturbate more than women.
Premature ejaculation is more of a psychological problem than due to excessive masturbation. If you are experiencing pre mature ejaculation you need to find out the cause. It could be due to fear most of the times. Fear you are going to be caught, especially when sex not with your spouse.
There are some steps you can follow, like you can use condoms which is lined with some anesthetic lining, this will put of ejaculation for a while. You can apply some analgesic spray called PSD502 available, this will help. You can try applying pressure eon perineum, this also helps.
Before this entire try putting off non sexual thoughts from your head, reduce anxiety if you have any, you can also try edging pressure.
If none of these help I suggest you consult a sexologist.
Thank you.