Ectopic Pregnancy help?

AF regular, last AF 3rd - 7th of May. Had intercourse 16th, 17th & 18th. Been having cramps ever since 17th, mostly on left side, CM everyday, different texture everyday, no spotting except a yellow tinge in a lotion like CM yesterday. Went to the doctors this morning, did a blood test for HCG levels. 
​HCG levels through a blood test to soon? He also mentioned a possibility of ectopic pregnancy, but I haven't had any spotting? Confused and worried, will find out this afternoon but needing some insite!! 
​If HCG isn't detected after blood test is there still a possibility? And what are the chances of ectopic?