The job market is quite competitive, especially retail. You are competing against those who may have more qualifications or more experience than you. That being said, you still have a chance, sometimes it is just good luck that you are offered the role. Sometimes it is who you know?
You say that you are only able to work Wednesdays and weekends, which could be another reason. Employers prefer someone who can be more flexible. Is this something you are able to relax on?
Are you currently looking for work or going into further study? If you have a lack of experience, looking for volunteering in the meantime may be a good idea. It doesn't look that good to have gaps of unemployment and it does show to bosses that you have the initiative to do something useful. It also teaches you skills and gives you a reference. Sadly, not many jobs offer feedback (too many applications, too busy). If you want to, you could contact them yourself. Also, have you got anyone to check over your CV? Sometimes a fresh pair of eyes can bring up ways to improve it.