Hi welcome to healthcare magic.
Unfortunately I cannot reassure you that you are 100 % safe from getting pregnant, although the possibility is very remote.
To get sure that you are not pregnant you may have a blood test
for hcg ( it may indicate pregnancy
one week before the expected period ). Then you may repeat it a couple of days later.
Another way is to wait for spontaneous menstruation
which will be a sure sign that you are not pregnant.
Do not rely on symptoms because as you said, your anxiety
may play a role.
Dr. Ahmed Bahaa.