What could this be??

I'm 17 years old and freaking out. My last period was on January 4th. And my next one was supposed to be February 2nd. I am sexually active but we use condoms and I know that things can slip up or something. I am now on the 44th day of my cycle and all pregnancy tests are negative. 😳 I have a runny nose and I've been having small headaches (which I never get) and nausea every now and then. And tired all the time. Can anyone help please?? I'm scared to go to my mom about it.