Loadinghalo

My question involves collection proceedings in the State of: Ontario, Canada
I really need some help and advice. I am from Canada and have been playing at an online casino for about 2 years now (located in Gibraltar I believe), I have won and lost money, made deposits by visa with 3rd party companies (swiftvoucher, PayR) as this is what the site uses in order to launder the money in I assume .....and I have also requested withdrawls (bank transfer) and got paid. Never had any problems. Well a few days ago I really messed up and the chronic gambler in me kept losing and losing and before I had realized what was even going on I had lost about $25,000 at blackjack....something is very wrong with me. I have no way of paying this amount back and am very desperate so I immediately cancelled my credit card before the charges were processed (I am assuming that they will still go through on the new card?). My next option would be to call my bank/credit card company(Visa) and dispute the charges saying that I didn't authorize the transactions....and say it wasn't me who made them this time. Would this work? Would they know what I am lying as all the previous purchases went through and were not disputed (for almost 2 years). These current deposit amounts however are way higher then anything I have ever done. Would my bank believe me? And if they found out I was lying what would happen? Most of my previous purchases were through swiftvoucher with only the last few days being the PayR option. What other questions would they ask me or would I need to sign any paperwork on the issue? How do disputes work with online gambling sites.....I have looked around the forum and see that it has worked for some people.....but their amounts were a lot smaller then $25,000. I have nobody to help me or nowhere to turn to to get the money. Could anyone with experience please help me as I am very desperate and have been having thoughts about hurting myself if I cant find a way out of this....please help.