Chemical Pregnancy? ? What is it exactly?

Hi ladies!

I am new to this whole ttc thing and I'm not quite sure I understand how a chemical pregnancy works.. I have 5 positive first response tests but I'm pretty sure I'm not supposed to start my menstrul cycle until march 23.. could that mean this is a chemical pregnancy? Or did I just ovulate at a didderent time than I expected? I'm sorry if I sound ignorant but if anyone can please help I would be so thankful! Btw for each test the pink line got darker with every test. I just really want to be pregnant! !