Whenever you go to a drill, don't actively advertise the fact you were medically discharged from ROTC. The only time you will have a problem is if you are mobilized you WILL need to disclose this at SRP, and they are very strict. You could have a broken toe and be non-deployable. If you wanted that badly to stay in the gaurd then a favorable second opinion from your primary care physician would maybe prevent a discharge from the gaurd. It is a long process so honestly I think you have nothing to worry about.