I go into a completely winning position and then blow it all.


What you describe is common. Everyone experiences this sometimes (and usually this goes in bursts too). Sometimes taking a break for a few days can help. Other times, it's just a cycle which you can't really escape other than trying your best and surviving through it.
Maybe look into how often you blow winning positions and analyze what the reason was to look for patterns. Are you "blowing it" by missing an opponent one-move tactic, or is it by outright hanging material (or worse, hanging checkmate), or is it a positional move where now you are losing? Difference causes will require different antidotes.
On a related (but not directly chess topic, check out this blog post I wrote).
https://www.chess.com/blog/KeSetoKaiba/chess-motivation-through-purpose

I'm reporting everyone who plays chess using an engine for cheating, so they can have their accounts closed. Stop doing this; play with your own intelligence. This will harm you and hinder our progress.

I'm reporting everyone who plays chess using an engine for cheating, so they can have their accounts closed. Stop doing this; play with your own intelligence. This will harm you and hinder our progress.
True, but it is against chess.com tos to discuss cheating in the public forums, so please keep all discussions around cheating in this club where it is allowed https://www.chess.com/club/cheating-forum
How to report someone on chess.com https://support.chess.com/article/209-how-do-i-report-someone https://www.chess.com/forum/view/general/how-to-contact-support-1