Someone Help Me?

Ok; I'm On The Pill, I Had Sex On My Week Off But My Period Come, I Didn't Take One Pill, But Had Sex That Day? I Was Due My Next Week Off, But On My Last Pill My Period Come Straight Away, Where It Usually Takes Three Days To Come, It Was Watery & Pinkish, No Period Pain Or Cramps Which Was Unusual, As I Get Them Quite Often Every Month When I'm Due. The Period? Lasted About 3-4 days, After This The Week Later, Started To Feel Really Nauseous, As A Dental Nurse Used To Seeing Blood, Now Can't Stand The Sight Of It & Was Instantly Sick By This, Which Was Unusual, Had Bubble Popping Sensation, For A Couple Of Days But This Has Now Stopped, And Sharp Pains, Which Make Me Stop What I'm Doing Only Last Couple Of Seconds, But Hurt. Becoming Quite Tired & Exhausted Quite Quickly, Constantly Hungry? Quite Paranoid About My Weight, And Notice My Belly Getting Quite Big, Hard Around My Pelvis & Other Areas. Could I Be Pregnant Or Is It In My Head? Help?