The simplest way if you can’t post original documents would be to just process your bank statements, that would be three documents assuming one per month, then pick up other information such as pending due as you have done or as @tut has suggested (which is preferable).
For any supplier payments on the bank statements, just put them to P &L Purchases so that avoids inventory, but at some point you will need to do a stocktake with valuations and then do an entry which adjusts the Inventory Account balance - refer to the guides for this,
It would appear that you don’t deal in account sales (debtors/accounts receivable) otherwise you would be in the same situation as pending dues.
What is of concern is your comment " finding information for the last 3 months". that is not a long time and would indicate that perhaps your filing of documentation is not what it should be. E.g. When you process/pay a supplier, their invoice should be filed in a lever arch file with A-Z indexing, that allows them all to be in one location. Depending on the your businesses activities, other items such as bank statements could also be filed there or in other lever arch files.
Can I suggest that If stress of work is such that the administration side is not quite up to scratch, then an economical solution is to engage a senior high school student (possibly doing bookkeeping) or a stay at home mum for a hour or two each week/month - you will be amazed at how this little bit of support can change the functioning of your whole business.