I took 2,000 u of hcg on 8/16, 8/18 & 8/20. its now 8/28 & im getting positive pregnancy urine tests this am. could it still be the hcg shot in my system? i know it has a half life of 24-36 hours but does bmi affect the half life? i have a low bmi?

I wonder why you did the urine pregnancy test. Was your period expected between 8/20 and 8/28? I would not trust this result and I suggest a retest at least three days after your expected period does not occur.

HCG may still be detected from the multiple injections, so a serum HCG level does not necessarily indicate pregnancy, since HCG will not be made even if pregnant in significant amounts until about 12-14 days or so after the HCG injections.