I love him, and I want to make him happy (he's really great with handling all of my physical limitations and stuff), but I'm simply not interested in sex, and frankly I'm kinda scared of the idea. I'm chronically ill, meaning I get exhausted very easily and get random adrenaline rushes while doing anything sexual or physical, which makes me even more exhausted and unwilling to try things.

Obviously we're both still young and have plenty of time (in theory), but he is getting frustrated and is unsatisfied with masturbation. He wants more from me physically, and he wants me to try it, even if I can't go very far.

I want to please him and help him out, but I'm also terrified. I've explained all of this to him and he's really understanding but at the same time he's frustrated and it's making me anxious. I don't want to ruin things by not being able to fulfill his physical needs. 

On one hand I've finally gotten my self esteem high enough to tell myself, "you deserve better; if he is only interested in the physical and doesn't care about your limitations, leave him." On the other hand, I love him and this is the only area we've struggled in. He's not mean or inconsiderate, but he legitimately has a very high sex drive, whereas I have none. I know that if I start helping him out then he'll expect it, and I don't want to feel pressured into having to do it often. 

I'm just so confused on this and really anxious/depressed over it. It doesn't help that the anniversary of my dad's death is coming up this week so I'm really emotionally unstable (I told him that as well). 

Can anyone offer some advice? I can try to rephrase things if need be; I have trouble keeping my thoughts organized.