What Causes Vaginal Spotting Along With Abdominal Cramping And Nausea?

Hi My Name Is Tiara My Period Started On March 9th Ended On The 12th Had Sex The 13th-14th He Ejaculated In Me Both Times I Thought My Period Was Not Supposed To Come on until Today The 14th So I Went To The Bathroom And Saw That It Was A Light Pinkish Color Stomach was hurting And cramping lastnight And A Little Today Also Nauseous Feeling Nervous Because I Never Been Pregnant Before And I Have No Clue What s Wrong