Might be filing for bankruptcy…
I have a substainial amount of credit available, and due to illness not receiving my normal paycheque. If I use money off the cards now and then in the near future file, will they charge me with fraud or be able to come back on me some other way?

In a bankruptcy all creditors automatically file with the trustee a list of all transactions in the previous three months. However, if the creditor believes you have abused the credit, they can review transactions for at least a year in the past, and longer if warranted. If the court is satisfied that you purposely ran up the current debts prior to filing they could either order the debts survive bankruptcy or require you to pay a significant amount of money into your trustee to compensate the creditors for your behavior.
I strongly recommend not running up the existing amounts, you are much better to meet with a trustee now, get the whole process finished quicker and avoiding any potentially difficulties.