There are many spammers who make their messages appear to come from the recipient as a way to bypass spam and security checks. You did not explain your problem, so I had to just guess.

All new messages like this one even that Mozilla sent me say they are from me. and at the very top of the new message above the tool bar it is indicating "Write mode"

I composed my first email on Thunderbird last night and i think i changed a setting by mistake and so all incoming new email messages are saying they are from me.

At the bottom of the new message in highlighted yellow it gives me this warning:

"A unique identity matching the From address was not found. The message will be sent using the current From field and settings from identity ___________________" (it lists my name and email address here)

At the top of each new message it says I'm in "Write" mode as if i'm replying to myself.