You can use sshpass if you are the only user of you system. But it's definitely a very bad idea. Everybody could get your passord if he has a shell access to your machine.
Once you can't useexchange public keys authentication. I suggest you to use expect. You'll need to secure an exp file containing your password. It will be stored on your hard dickdisk, so every user having the sudo or root access can hack it. But at least it's really more secure than sshpass.