What Causes Headache, Stomach Cramps And Back Pain?

hi doctor, I am a 18 years old female. since 3 days i have been experiencing some bad headaches, stomach cramps, lower backaches, nausea around food, feeling of wanting to throw up and very tired. I am on my period but normally I only experience lower backaches when this time of the month happens. I am sexually active and my mom thinks that my symptoms are very close to a pregnancy... Maybe you can help me out in telling me what I might have.