Absolutely clueless!

Ok so I'm 20 and in my 5th week of pregnancy! Ive worked out my due date will be around the 18th march, It's my first baby, and I'm absolutely terrified already! I don't no what to expect and when to expect them! Not really felt any symptoms other then very very tender boobs! And a few campings in my stumach! They feel abit like period pains... When does the sickness kick in?