While you study, find your limits. When you understand when you need to take that small break from studying, take it.
When it's about your mother, all I can say is..keep going and do things at your pace. Sometimes the people closest to you, hurt you more but that shouldn't mean should feel down and give it all up. People study their own way and learn at their own time. So take your time.

Also, here..you said you needed help. Just in case you are getting thoughts of suicide or self-harm..you can call here to speak with someone. (800-273-8255)
They will help you. This is not a forced thing, this is only if you want!