Ok so I had unprotected sex 30 days ago and ever since I have had sensitivity on the head of my penis. At times it's just annoying and other times it is very painful. Along with this I do have some burning when I pee and it seems to get worse after I masturbate. I already got tested for most std/sti's other than herpes all which came out negative! And there are no noticeable spots or anything on my penis