Grief, loss, and suffering can cause long term emotional pain, and the stress of such may also be causing clinical depression.
Especially given your lack of confidence, desirability, and such.
Not that identification of that issue means there is a fix for the issue, only that you consider if perhaps you are depressed? However, trying to treat the depression directly can lead to multiple positive side effects independent of your ability to get a new sexual partner.
It's something I've observed in my own, and my wife's, lives multiple times (and, sometimes, seen the cause of as well!)
Try to address that too (not necessarily first, but in general) if that is a problem because it will be an overall drag on your whole life otherwise.