If someone slaps or punches you once and you KNOW you cant fight because you would for SURE lose can you call the cops and what do you say if you do call them?

Yes. Call the cops and tell them what happened. That said, if it's been awhile, there's not much they could (or would) do, but at least if the person ever causes trouble again (with you or somebody else) then there'll be a record of what they did to you. If the person is a family member or significant other or has some other familial relationship with you (baby daddy, etc.), it may be domestic violencel and the cops/prosecutor may be more willing to file formal charges provided you are willing to testify in court. Just remember that once you call the cops, you can't "uncall" them just because you don't want to press charges anymore. They will write a report, it will probably go to a prosecutor who will make a decision as to whether or not to proceed with a case. If they decide to file formal charges, you will be subpoenaed as a witness against the person who hit you. This could very well happen whether you want to keep on with the case or not. Once you get "the system" involved in your life it is very difficult to get it out of your life, so make sure this is something that's worth it.