It may have to do with the medications you are taking. I remember when I was younger I changed my medication to focus more and it made me extremely moody and sad. Maybe talk to your doctor about alternatives if your medicine is making you feel that way. I know you mentioned that you have been taking the same medication for years but its possible to outgrow your meds. You may need a higher dosage or a whole new prescription all together. I hope you figure this out. Believe me I’ve been there it’s not a good place to be in. You are not alone.
Best of luck!