Can implantation bleeding happen 1 month after conception? i'm on day 42 no sign of period but brown spotting. is this implantation?

Possibly: You may have ovulated late, so this could be implantation bleeding or it could represent other problems e.g. A tubal pregnancy. Please see your gynecologist.

The brown spotting: Might be your period. Brown discharge is usually older, deoxygenated blood being cleaned from the uterus. Implantation does not occur a month after conception. It usually doesn't occur but when it does - it is usually just a drop or two of blood.