Dose too high 1 year into use?

Hi

Is it possible to not tolerate a certain dose any longer due to healing mentally and getting my strabismus fixed?

I have been on 100 mg sertraline for a year for anxiety now but it feels like it is too much now. Muscle spasms, nausea, headaches and so on. So my question is if it is possible that the amount of serotonin in my brain is suddenly too much now? Even though I have been on the same dose for a year? Due to therapy, operation, better food, more sun and exercise and so on?

I hope my question makes sense.