ADHD Medicine with least side effects

I have an 11 year old boy with ADHD..been on meds since 5 years old. We've had issues here & there about him taking his medicine because he says it makes his tunny hurt,he can't eat & he has no personality/quiet the whole day,etc. This year we did a trial run of NO meds & he's so behind after only 2 weeks of school. Disorganized,forgetful,& not focused so he's not "learning" or "getting" what's being taught in class. He's a super smart kid going to traditional middle school (graduated from traditional elem school) & there hasn't been any major hard work yet. I told him it looks like the no meds isn't working. He cried because he says he can't eat & he can't on meds. He goes ALL DAY until 9pm nothing. We have to make him drink even. He also says he's not just calm he's no talking,no taking part,won't talk to friends & for a while when he comes home..no playing until meds wear off. I feel so bad for him. We all want our kids happy & "normal". I give him the talk of this is hard but he's blessed this is the only health concern he has since he was 3lbs/preemie. He knows it could be worse. He knows that these side effects vs failing 6th grade..meds win. I am wondeimg if there is any ADHD meds less likely to cause these side effects. He isn't hyper anymore (seems to outgrown this) but can't focus,bad memory,disorganized,etc). Any advice? Thanks so so much. I was in tears last night. I feel so overwhelmed with work,single mom & trying to get him caught up,making him DO homework, & feel alone @ times. Thanks for any help.