thyroid meds start affecting you by 6 weeks ,if you have lost weight or felt nervousness,palpitations,loose motions then these can be due to meds,and now if you come to 25 from 125 then your problems if there are any will take another 6 weeks to stabilise after correcting the dose,i advise that you get a thyroid profile done now immidiately and then start with 25 mcg dose and repeat after 6 weeks,meanwhile please get you bp and heart rate checked.

In case of overdosage of thyroid medication, you can experience weight loss, palpitations, anxiety etc. However you need to get your thyroid function test done and consult your doctor inorder to analyse the effect of the previous dose and decide the further course of action.