Is it possible for a beta hcg to be wrong--by that i mean to actually be pregnant but the hormone not detected? does it happen even tho not likely?

Any test can b wrong: Most likely, however, a beta HCG test is correct. Urine tests are less reliable early on in pregnancy, but blood tests are usually right on. That's why we use the (for sure) blood test as a backup for the (pretty for sure) urine test. Of course, there may be any cross-reactivity or contamination of any test rendering it inaccurate, but the chances of that happening are remote.

Noy usually: Because a beta HCG measures down to 5miu HCG which is extremely accuarte, u could be a few days preg right after conception and it may not show up yet, but once u are close to the missed period or at the time tehb missed period should be the blood HCG will be +.