I'm a 16 y/o teen and I have a small problem, when I make love with my girlfriend, I don't have the feeling to come. I can last 25 minutes + without having the feeling to come. And I start to hurt her because it lasts too long. Is there somebody who can help me? Is it because it's my first sexual relations and that i'm too stressed or something ?? I would really appreciate some help 
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Thank you.
If you're using a condom,that may be why. You might want to switch to a thinner/more sensitive kind.
Also make sure to relax and not to tense up and get nervous.
You also may need to make things more exciting, such as making sex more risky, meaning there being more of a risk of getting caught or being seen, or just changing things up a bit. Check out other positions too.
you could just be nervous, its not a big deal, try new things, more foreplay, be adventerous. Also, if you masturbate a lot that can be a big reason for this, try not to mastrubat so much.