Hi Everybody,

I have a dumb question about mining my own transactions.
One month ago, I transfered my btcs using a old software and the fee for mining went with zero; So, four days, five days, six...  and nobody confirmed my transaction; So, I made other transaction with 5 USD to mining my transaction and invalidate older.
It's not right, I know, but I was desesperated.
After this day, I think about it everytime and one question doesn't go with my head.
If I mark my transaction on blockchain and confirm this 6 times, this transaction can be validated. What happen if I confirm 6 times a double spend or one invalid transaction with fake coins?
Imagine that if I pass for one exchange wallet this with zero fee and confirm for my own transactions and there, I change for other coin and withdraw.
Where is wrong my thinking?

Tks