Are there any types of pregnancies that don't show up on home pregnancy tests?

The home pregnancy tests only look for the hormones released by being pregnant.

As it takes a while for hormone levels to raise to a suficient level for detection, this might be undetectable in the very early part of your pregnancy.

As pregnancy carries on, this will most always show up after 4 to 6 weeks.

If you are unsure, then you might want to have a "professional" test done at a clinic.