Pregnancy symptoms?

Long story short, my boyfriend and I are both in high school. We've been on and off for almost 4 years now. We've had sex a ton of times and we never use condoms, we just use the "withdrawal" method. I've never had and worries at all. But sometimes i have a tendency to stress over it and i just wanted to know if anyone had anything that would be useful for me to remember just in case there's a chance i may need to worry in the future. Anything such as pregnancy symptoms and such would be helpful.