hi thank you for asking your concern and welcome to HCM. there are very few chances of getting pregnant after tubal ligation but it depends on the type of surgery also but lets forget about it and still chances are very less. amitryptilline itself cause weight gain after this much of use. regarding missed periods and you have already done UPT which came out to be negative there is almost no chance of any worry but still sonography will be helpfull to rule out pregnancy. if sonography comes out to be normal then there is no worry as missed period is not a problem if occuring first time. it will regain to normality after some time in most of the women. if repeatedly missing then you need to consult a gynecologist. i hope i answered your concern if any doubt please ask us regards dr. abhijit