when I mouse over the sender address on some junk email it shows my email address. when outlook opens that address info it access some of my old emails. What is going on? is this a security problem?

Probably someone that has your email address has some malware and it stuck you randomly to appear as the sender and you just happened to get that one. Others may have gotten it too. Doesn't mean it came from you. May go on for a day, then it will stick someone else's email on there. The idea is to throw people off so they don't know who has the malware.
Never click on emails like that! You can check the message source info and maybe figure out where it really came from.

What RK Said. You should be fine.

You can test your old email addresses and passwords here: https://haveibeenpwned.com/
They basically collected all the user/password databases of major breaches of the past decade.

That aside, if you see your own mail address as "the sender", it's probably simple email address spoofing.

thanks guys, I googled "from spamming" and see how common it is. stuff like this makes me less inclined to use the internet!

I just ran that link and it said I have 8 breaches. I guess I need to change some passwords.

You probably do. Most people should, actually.