Welcome to HealthcareMagic forum .
Please do not panic.The chances of you being pregnant are very less and the symptoms seem more likely due to premenstrual changes& stress
First of all let me tell you that even with precum there can be pregnancy
so it's definitely advisable to practice safe sex
every time and preferably try to avoid any high risk behaviour till you are adults for the best interest of both of you.
You are most likely safe if you have used contraceptive
and washed yourself after the accident but do not take chances and get a urine pregnancy test done if your periods are delayed by a week from due date.
As of now don't worry as stress may further delay the periods and increase your dilemma.
Hope I have helped you.
Wishing you good health.