Troubles finishing :/

[Camfer]

Oh and another thing, I've seen guys jerk off by squeezing their cocks so tight it's as if they're swinging a pick ax in a coal mine, then pumping it up and down as fast as a jackhammer.

If that's your masturbation technique, then it might be worth exploring the other end of that spectrum, which is slow with a light touch. You might have inadvertently trained your cock to shoot only after a certain type of extremely vigorous stimulus. That can be unlearned.

So keep exploring and changing it up.

[Darius]

Hey Killer! We're guys, we like to cum, so it would be frustrating if you can't cum by what you are doing.

My guess is that the problem might have more than one cause. As Mike mentioned, your dick might be so used to the grip of your hand that anything else might take time to get used to. Lots of guys claim they can't cum from a blow job.
I don't know about your ADHD, however. Have you researched that or talked to anyone "in the know" about it?

Most importantly, you guys love each other, so being able to talk about anything is important. If the problem is stress related, then getting it out in the open is important and will likely help. Just tell him what you told us and be sure to let him know this is just how your body works and has nothing to do with how he turns you on. This is not just your issue, it belongs to both of you. As a bottom, he is enjoying you being inside him. Your cumming inside might be the happy ending he wants, but it doesn't really make a difference in his pleasure.
Just do what the two of you like to do for pleasure, then have him help you finish other than in his butt.
Have you tried having him use his hand on your dick and balls while you are inside him. Maybe that added touch will help.

[Virge]

Oh and another thing, I've seen guys jerk off by squeezing their cocks so tight it's as if they're swinging a pick ax in a coal mine, then pumping it up and down as fast as a jackhammer.

If that's your masturbation technique, then it might be worth exploring the other end of that spectrum, which is slow with a light touch. You might have inadvertently trained your cock to shoot only after a certain type of extremely vigorous stimulus. That can be unlearned.

So keep exploring and changing it up.

↑↑↑↑ This is not only very true but very important... and pretty easy if decide to reteach your weenie to like other stimulation. With a partner.. all you have to do is stop jerking yourself off and let him do it... Don't worry, you'll start liking it better real fast.

One of the really hard things to "unlearn" is that two separate nervous systems control orgasm and ejaculation. In other words they are not the same thing and you can learn to have orgasms with ejaculations... and the younger you start the easier it is...

But you need to get past this first stage in the learning curve and become more comfortable and easy about sex, penetration and other teen angst.