From the AT Command set,<CR><LF> are sent from the module before data(message) is sent.
So, try to collect the entire reply given by the module in an array.
After time delay, check from the array the character <CR> which is decimal 13.
Then, from the second character the message starts.
This code snippet may work:
do
{
q++;
}while(gsm_response[q]!=13); //<CR><LF>MESSAGE<CR> 13=<CR>
for(q=q+2,temp=0;gsm_response[q]!=13;q++,temp++)
{
message[temp]=gsm_response[q];
}