It is different for different people. Some people tell them right up front the minute they talk or see them. Others wait a month or so, some wait a few months. It is just a time thing. You'll know when the right time is.
If for some reason after you disclose your status and they freak out about it, you can try to tell them the facts. If they do not want to listen to the facts, then just let it go and let them go, they will not be worth it in the end.

i tell them before anything physical or any mushy stuff begins

Yea i agree. Im scared if i tell this guy ive been talking that im positive he might stop talking to me and tell everyone. Its only been a month though. So i shouldnt feel bad foe not telling him?

Well I suppose luckily my ex husband made my status public via social media (he is facing felony criminal challenges) so my case is easy.

But I wouldn't tell them until some trust is built up. Much like we don't share other parts of our lives until we feel safe