PLEASE HELP--Can STD symptoms show up in 12 hours or less

I just had unprotected sex with my bf, it was our first time sleeping together...within the few hours afterwards he started asking me if I was sure I didn't have any STD's because he has now been itchy down there like crazy  since pretty much right after.  I don't  sleep around but found out that my ex had cheated on me quite often and had a lot of past partners....so I get tested frequently and so far it's all negative but I also know that sometimes it takes some time to test positive for STD's even tho uve contracted them months before...   Can symptoms show up in that short of an amount of time?  Or could this be a symptom of something preexisting that he has?!

[Vance2335]

No this is not a STD issue.

[JessyJames2010]

Hello

His symptoms are not indicative of an STD.

It is likely that this is something pre-existing that he has.