Don't come off anything cold turkey, at best you will ramp up the pressure on yourself, at worst you will make yourself ill. Usually the advice with psych meds is that it is OK to drive if they don't make you drowsy. So try to get some good rest to minimise the chances of that happening. If you can get a doctor's appt before your medical then try and do so, he can advise you on tapering down on the meds if that is what he thinks is best.

Don't worry about having given in your notice, there is always a reason for things happening and the reason is the old job was making you ill, you were at breaking point. Without the pressure from that job, you will be able to see your way through far more clearly.