Pregnant???

So my last period was the 17th of April. But before my period i had sex and after my period i had sex more than once. Is it possible that i could be pregnant and not know it? I have been feeling really nauseous for the past three weeks coming up to four weeks now and I’m always feeling tired, I’m not hungry when it comes to breakfast, lunch or dinner, but I’ll eat a lot before bed. Any suggestions or advice would be great and if possible that i am pregnant how do i tell my parents?