Usually, it should not be possible for any third party to change your password unless you have earlier shared your login and password details with such third party. Usually, there is always a feature on such websites to again change the password if you suspect that your password has been changed or hacked. Depending upon the features of the website, you can use the feature of "Forgot Password" and the system may generate a new random password for you and may mail it to you at your registered email address. If there is a different procedure at the e-filing website, you may follow that procedure for change of password again. If needed, you may take help of the concerned IT authorities to change your password again.
But, next time, you should not share your password with any other person if you don't want it to be compromised or changed again without your permission. You may of course file a complaint for unauthorized change of your password since it is like hacking which is an offence under the Information Technology Act, 2000. However, you'll have to provide proof and from the details given by you it appears that you had shared the password with your wife / advocate.