I had my last period on the 16th Feb, I had unprotected intercourse from a week before up to the night before my period. My normal cycle is around 5-7 days but my last one only lasted 3 days, I had normal bleeding the 1st day not so much on the 2nd and a bit of spotting on the 3rd day along with this I have been feeling sick, going to the bathroom more often, headaches and backache. For the past week or more I have been having abdominal cramps a bit similar to period cramps but a lot more painful, tonight I have had a bit of spotting, my periods are usually 28 days but the past 4 I have had have been 3-5 days late I have never been early before. Is there any possibility I could be pregnant?

It's certainly possible... see what happens when you would expect your next period and test accordingly.