Any ideas or can someone be of assistance? I really don't know what to do
TL;DR: Your money has been stolen. There is nothing you can do that has any significant probability to recover your $660.
The thief got access to the private-keys stored in your wallet.
a transaction sometime in March of 2019 was made and I didn't make any transactions in March
One possibility is that someone gained access to your wallet and stole your money.
One recent issue was with the Electrum wallet.
However, if you have a PC wallet or access an online wallet from a PC it is always possible that other malware on your PC stole your passwords and used them to access your wallet, steal money and finally erase logs and data to cover their tracks.
I have put my receiving address into [a] block chain [explorer]
Most modern wallets are HD wallets that create a new receiving address for each transaction.
I created new receiving addresses which I read can sometimes [make] your available bitcoins appear.
I've not heard of this, it would have to be a bug in a specific wallet. In general I would be surprised if this helps.
If you found unexpected transactions in a blockchain explorer, it is unlikely that there is a fault in your wallet software. More likely you are a victim of theft.
If your wallet is misbehaving. One solution is to make a careful copy of your seed-words or your private key (you should have these already in a safe place), then use those on a fresh computer (or phone etc) to download and install the wallet software from the only genuine trusted website and make a new duplicate wallet and let it synchronise fully. You don't need to erase your old wallet until the new one is working fully.
it is safe for me to paste my receving address here
There are potential privacy issues if you only use one receiving address. Anyone can see a list of all the transactions made involving that address. But it doesn't give anyone any way to access your money.
You can also safely publish a transaction id and the name & version number of your wallet software (e.g. bitcoin-core 0.18.0, electrum 3.3.4, ...)
Never give anyone your private key, your seed-phrase / recovery-phrase or the password to your wallet or online wallet or account. Changing a previously disclosed password does not re-secure your wallet/account.
Also this is what I read regarding created a new address can sometimes show balances again: reddit.com/r/Iota/comments/6sim7o/
That advice relates to IOTA not to Bitcoin.
I'm positive that I never used bitcoin this year
Everything suggests your Bitcoin was stolen.
I wouldn't use that wallet again and I wouldn't use that PC for any new wallet or any further financial activity again. Even after zeroing the disks and cleanly reinstalling the operating system, I'd worry about BIOS malware, infected USB devices, etc.