sewing machine help

[bludog.livejournal.com]

Hi all! I hope there is someone out there who can help me. I am pretty new to sewing machines and I am trying to make something rather simple. The problem I am having is with using the machine. When I go to sew the stitches are not holding and the underside (coming from the bobbin) is all messy, no clear stitches. I have it threaded properly and have re-threaded the machine. What am I doing wrong? I am very frustrated. Thanks for any help.