now for my usual googled dream interpretation:
Dream spiders are enigmatic, much like their waking life counterparts. On one hand, a spider may be seen as venomous, poisonous and as such may indicate a poisonous aspect of yourself, something causing you to engage in self-sabotage. Or it may indicate a toxic relationship, one that has an insidious hold one you, draining away your life force. It may also indicate that you feel trapped in a situation or relationship. On the other hand, spiders are stealthy creatures who patiently wait for the right moment to take action. In this case a spider may be urging you to follow its example and hold off taking action until you have carefully gathered all the facts
Look at the action of your dream spider and your own associations with spiders. If you fear them intensely, it is likely that the spider is appearing as a warning or it is appearing in its negative context.