Couldnt get hard

You are likely suffering from performance anxiety. It basically boils down to you being so worried about things going "right" and everything being "perfect" that these thoughts impede you from enjoying yourself and getting in the right mood to keep your boner. It makes perfect sense that you softened as soon as your boxers dropped since you were then gonna take an active role ("showtime") and that's when the worries and insecurities start to pour.

Since, as the name suggests, performance anxiety is purely a psychological obstacle (your brain is basically sabotaging your body) the best solution is for you to find a way to relax. One thing I think applies to everyone is letting go of this porn-like ideal that everything has to go down in a specific way in order for it to be "good sex." It's ok if things get awkward, it's ok if you are a little sloppy at first, it's ok if you need some time to get things going down there, it's ok to talk and ask questions if needed, it's ok to voice your displeasure if your are not comfortable with something. There is no rule-book for sex, and it's certainly not a test nor a competition. It's supposed to be fun, so forget about qualifiers, imaginary parameters and/or whatever you think "good sex" is supposed to be and have fun.

Body image issues are another factor that can induce performance anxiety. Being comfortable with the way you look [naked] will certainly help you have a better sex life.

Of course, just to be sure this isn't a medical problem (like erectile dysfunction), you could always consult with a doctor. If you are taking some medication, that could also be affecting your sexual performance (dem side-effects), but, again, you'll need to talk to a doctor for confirmation.

 

How are you when you masturbate? Can you maintain an erection? If you can, then it shouldn't be a circulatory issue. I do agree with Snake; it could be performance anxiety.

If you can't keep hard, then takes things slow. Maybe the issue is you having to go naked during intimacy - try sex with your clothes on/partially on.

 

Have you always had this problem with getting hard while masturbating? Or did it only just start after your first attempt of having sex?

 

Well I can tell you one thing, stressing over it is not gonna help (it may be the cause...).

Get checked. Finding out for sure whether the problem is physiological or psychological is gonna give you some peace of mind and help you tackle the real problem better.

I know it can be embarrassing to talk to your parents about this, but they will understand. We are all sexual creatures, and as such I can assure you it won't be too much of a shock for them to find out you are thinking about these kind of things now. Everyone knows teens are horndogs, we are not breaking new ground here lol. You don't have to tell them that you have attempted to have sex already, just let them know you think something may be wrong with your penis and you wanna get checked just in case. You'll have to deal with it at some point, better to do it now and get it out of the way.