As mentioned in other answers, including it is much more likely to help you than omitting it, because an unexplained gap in your CV can be suspicious. (Were you unemployed? Incarcerated? Or do you have a job that would look even worse than those??) That's something that would almost certainly come up in an interview (if it got that far).
A very short period of employment doesn't look great, but it's not necessarily a red flag, as long as:
- You can provide a reasonable explanation of why it's so short. (This could be along the lines of “I didn't fit into the company culture,” or “The work wasn't what I was led to expect.”)
- You don't have many short periods of employment.
Basically, you need to allay a prospective employer's suspicions that you might be quitting them in a few months too.
And, as explained in many other answers on this site, it's usually better not to say anything to your current employer until you have a signed offer that'd you'd be prepared to accept. (And almost always far better not to resign until then!)