Man, it must be so frustrating to care so much and have it not be seen, or provable.

I had a boyfriend that described things similarly to you;
It might have been a reassurance thing for me, but I really loved to cuddle and spend a lot of time with him-that's how I interpeted care. But he could go on his computer and be happy discovering, creating, etc for weeks, and then I would feel like he didn't care about me, and I would also get mad at him when he did come back to me, because I had felt unloved and abandoned, at the time.

It really did feel like it was if he was "gone". We even tried to schedule time to be together, but now I understand, when one is in that mode, it's like ripping a songwriter away from his composition in the middle of the creation of his masterpeice.

I think it would really help if you could voice your struggles as much as possible to your loved ones, (especially?) your partner. Confiding in a person is an intimate activity, and your post was actually very intimate and deep;
It may take a lot of energy at first, but like exercise I think it could get easier for you over time, especially if you're with someone who is supportive.

I'm not sure if that's the type of problem that you are dealing with, but if it is I hope you are able to find someone who doesn't pull for you to change, but can let you be who you are; there's a balance somewhere-it's just finding it that can drive us crazy!