17 & Pregnant

I'm worrying as I don't know how to tell my parents.  I'm 17, still in college and I want to go to university. I know it'll be hard but I know I can do it. 
My problem is, my mums pregnant so I'm scared to tell her I am. I'm only 5 weeks so I do want to wait until I'm at least 12 weeks to make sure I'm in the safe zone, but how do I tell her in the end?Â