Overthinkers unite!

So I overthink absolutely everything.  We have only been TTC for three weeks.  One night we had sex and pretty soon after I had a major nausea wave that lasted a couple of hours.  I woke up feeling a bit sick too.  Of course, I immediately start thinking that I'm pregnant.  But then of course I start second guessing.  'There has to be another explanation.' Days pass and more sick feelings, but more thoughts.  'Maybe the nausea is all in my head.'  'No!  I'm totes pregnant!'  'But your boobs aren't sore.'  'But I'm sick and have weird cravings and stuff smells weird.'  'You're imagining it.'  'But, babyyyy...'