Pregnant from precum?

Okay ladies I'm pretty sure this is not the case. I've done some research and it seems practically impossible but let me explain my situation here. 
I was put on the depo-provera for endometriosis, well I'm not a fan of how it worked with my body. I've heard that shortly after being off of it you can be super fertile. I don't actually know. 
Anywho my boyfriend and I got a little carried away and he put the tip in...but then figured that no "rain coat" equals no "playground".  Kay cool no biggie......
3 weeks later and my boobs are stupid tender, I'm nauseas beyond belief and I'm craving ramen noodles (last time I was pregnant [miscarried unfortunately] I craved ramen noodles.)
Anywho! Talk me down ladies! It's impossible right?