ok so if im getting this right
youre prescribed ritalin for the last 12 years and now you cannot focus with it because your tolerance?
college can be an extremely stressful period for anyone add or adhd or not, so i can certainly sympathize with your efforts to wanting the ability to continue your studies in a productive manner.
since it would appear you have no interest in quitting your prescribed medications
you should first and foremos
t speak with your doctor while we have many health professionals on board were not your doctor we do not know your history it is apparent your medication is not working effectively
secondly you need to realize you cannot rely on medication all the time to make yourself productive, you need to learn how to focus to your best abilities in able to succeed in your studies this isnt going to come overnight and certainly will most likely be something you need to constantly strive with.
I also suggest working with a peer to peer tutor in school, not because you need tutoring but because you need someone who can understand your current mental state and keep you focused on the right track, usually colleges provide peer to peer tutors at no cost,
those students are there to you, so take advantage of it and use it.
Another suggestion is a mental health counselor in your tuition fees you have a plethora of student needs that almost no students use because they do not know they are there.
There is most likely someone who is a mental health counselor there who can help you create goal settings and action plans in order to help you succeed.
heres a few tips for self success
http://www.additudemag.com/adhd-web/article/5197.html
I would suggest you take a break from marijuana, clearly at this point youre just at a tolerance level too high and you need to take a break it is most likely not from the ritalin itself, breaks in marijuana can be beneficial , just take a week or two off it.