What Causes Pregnancy Symptoms After Unprotected Sex?

Hi im Dustee Pickett im 14 and have been experiencing pregnancy symptoms i have had unprotected sex 4 times with the same guy and my breats have been hurting, severe headaches, bloating, fatigue, mood swings, and have had to go to the bathroom alot. I have took 3 at home pregnancy tests they came back negative. But im also on the depo shot which i read online can give a false reading it could say negative but you could still be pregnant