Need advice please help!!

[privatetrey]

I was accused of shoplifting perfumes got charged going to court but the problem I have is my friend admitted shoplifting and was given a caution and this is making everything difficult as I am pleading not guilty and the security guard is saying he saw me stealing. I been advised to get the receipts for the perfumes but I can't as I don't have any. I wanted to change the perfumes for the ones I want but lady refused then the security guard states I stole them in the shop on the day. Now it's my word against his but there is an issue of my friend admitting stealing.What chance have I got and what advice can u offer. I would appreciate any help as this is stressing me and am a new qualified social worker and can't sleep with stress.