Can't climax during foreplay?

Title says it all. I'm in my late teens, jack off I'd say, 4-5x a week. I have no problems with ejaculating by masturbation. However, with a girl, I just can't finish. Its not that it doesn't feel good, I just can't get to the climax. I didn't use to have this problem, but I had like an 11 month gap between last sexual relationships :/. So i'm wondering, what to do. I'm left feeling inadequate and shitty. I don't have any weird fetishes or anything, i'm circumcised, I don't know what to do. Do I grip too hard while jacking off? Have I desensitized myself? I've gotten like 3 attempted handjobs and a blowjob, I can't deal with this any longer.

I'm around 16 years old by the way if that helps, in good shape, on adderal and intuniv (both prescribed)