Did my braces give me a lisp?!?

So, I've always had perfect speech. I know that because my mother is a speech therapist. About 2 years ago I got braces, which I still have. A girl was just texting me, who is very insecure about herself. She brought up my "lisp" which I never knew I had. Know that I'm thinking about it... I kinda do whistle when I make an "s" sound. But I don't make a "th" sound. Is this even considered a lisp? Will it go away once I get my braces of? Is there anything I can do now that will muffle it? Thanks xx