i am 18 years old and i masturbate and some portion of penis head remains covered . so is it normal in sex like is that ok.
This is quite normal for someone of your age. Your penis will likely continue to develop until you are somewhere between 19 and 25 years of age. When you say ‘a portion of the head remains covered’ this would define that you have not been circumcised in any way? You do not need to expose the head / glans of your penis at all to function sexually in any way, if this is what you are asking?
If you are uncircumcised - that is no part of you foreskin that covers the head of the penis has been surgically removed - you can do stretches that will help your foreskin to become more supple so that you can, eventually, expose the complete glans / head of your penis. You would need to work on this for an extended period of months, rather than within days or even weeks.
If you choose to try this you MUST do these very gently for 3 or 4 weeks, stop if you experience any pain, then wait for a 2 or 3 weeks before you try again. If you get no pain, then you can slightly increase the pressure you use to do your stretches. Again, you gradually increase the pressure over a period of months, not days or weeks. As we cannot post external web site links on here, you will need to search for the following: -
Wiki > How > How to > Do > Phimosis Stretching
The automatic formatting of my message has removed the last part of what you need to search for, the complete search term is
Wiki HowHow to Do Phimosis Stretching
The original was also known as " Three ways to do phimosis stretching " on the same web site