If you have a trusted friend and expert in this matter, better to ask help right now. Because learning those above-mentioned steps will takes time for you to perform and I'm afraid if it was already been confirmed before you've done.
Its not that easy in reality. Tools mentioned above or just learning about it.
Been there, mistake of a transaction, tried many many different approach, none worked.
Its thousand times easier to double check before send/learn about security than trying to double spend.
Hope ur situation ended well.