I think what you need to do is post a small selection (two or three at most) of your failed photos under those conditions and provide the following information:
Shutter speed - ISO - aperture as well as detailing the focusing mode you used, any support lighting, the conditions of the shot. Also include how you went about taking the photo - how did you focus, compose and take the photo. Go through all the steps. Chances are you might be making more than one mistake which, whilst small on its own, is adding up to the increased problems that you are experiencing.
With those photos we can get a better idea of how you are taking your photos and where your problems are - without the info we can only suggest possibilities which might well just cause frustration since they might not be the ones that you are experiencing.
You also mention that you are disabled without (I think) mentioning the nature of this disability; I'm not going to press you to release such information if you don't wish to, but I know that some disabilities can result in increased trouble for photography - however there are often methods which can help overcome these (there are also several disabled photographer groups around the new who could further suggest ideas depending upon the nature of your disability).