This web site may be able to help you find a IV cert class:
http://events.nursingspectrum.com/event.cfm
I had similar difficulties when I began as a nurse. It took me about a year before I was comfortable starting IV's. I asked my nurse educator to take me around the hospital one day to start IV's. If they are not willing to help you, you should speak with your unit manager. IV cert. is helpful, but unfortunately starting IV's just takes practice