Looks can be deceiving.
I often refer to myself as either the "fittest sick person" or the "sickest fit person" to people. I don't say this to be arrogant. But I see myself as a great example of how your level of "fitness" has nothing to do with your level of "illness," and vice versa. Objectively you already know this to be true. A world-class athlete can come down with the flu. Even while they are sick, this person is still extremely fit. It's no different when you have a chronic illness, except for the fact that you are sick all the time. What's unfortunate is how this leads people to not understand how you could possibly feel awful, because you may look great.
What's actually been fascinating to me is how my level of fitness seemingly hasn't diminished at all in the five years I've been sick. Although this only reinforces my point. I can still be one of the top athletes in the gym, and yet feel like complete garbage while doing so. Don't get me wrong, it can be an absolute struggle to get there. It takes more energy than it used to. There are times when the world is spinning and all I want to do is lie down. But almost invariably a workout will make me feel better, even if only for 30 minutes. I'll take that over doing nothing and not knowing how I will feel. I like to believe it's a good idea to keep working out, but honestly I have no idea if that's true. But it's part of who I am so it's what I will continue to do.
So I guess the point here is to encourage you to exercise, even when it's painful. I don't have any science to say that's a good idea but I personally believe it is. Tougher people are harder to kill. So stay fit my friends, even if you are ill.