Had unprotected sex with someone i didnt know well, (10 seconds of penetration) about 4 months ago. would i have symptoms of std by now?

Maybe not: There are at least a dozen diseases that can pass during intercourse & some generate symptoms in most people within days/weeks. Others can pass to you & never have obvious symptoms. Of the big 4, chlamydia & gonorrhea can transfer & not have symptoms in many patients but quietly lead to sterility in women. If exposed, a screening for STD's is a prudent choice.