Hi, I Have A Question About Something That Happened 2

Hi, I have a question about something that happened 2 me today... May sound a bit odd but as I came back I seen my mom's friend's sister who is a very Beautiful beautiful attractive girl.. And I noticed she was wearing some really short shorts..improved how thick her thighs...bottom line instantly I began to notice that my face got really really hot considering it was cold outside n I felt as if my blood sugar dropped now had 2 catch my breath a bit.. Doctor can you please tell me why I got that physical reaction please?