PREGNANCY

So I need advice my period is irregular & the last time I had it was april 12 of this year ive been having unprotected sex but the irregular period was normal for me I didn’t think nothing of it . Now it’s been 5 months no period I took pregnancy test it was negative still wasn’t worried , because my period always been irregular I’ve been ovulating the doctors said , I had sex sep 4 and been conceived. 3 days later I was feeling ver nauseous and had to leave work early I took a test that day it was the 7 which was 3 days after I had sex not positive the obgyn told me try on the 18 , I’ve been nauseous no vomiting , back ache , cramping and blue veins in chest any advice ?