VS 2010 ssl and man in themiddle

hello
i'm new to ssl please help

in the beginning
my vb net 2010 program was sending a php request to my server with a sensitive data through regular http webrequest
it was easily monitored through regular tcp sniffers

so i bought geotrust ssl and installed on mysite.com
but with more advanced http debuggers like Fiddler, Charles its still vulnerable with the man in the middle attacks
i can monitor all sensitive data again :(

this is my example

webRequest = webRequest.Create("https://mysite.com/info.php?var=xxxxxxxx")
webresponse = webRequest.GetResponse()
inStream = New StreamReader(webresponse.GetResponseStream())
result= inStream.ReadToEnd()
inStream.Close()
webresponse.Close()

so the question is how to make this request not detectable by these advanced http debuggers?
if i cant fix it seems theres is no point for spending money on ssl

little googling told me about ssl validation , but i cant find any snippet for that
thank you so much