HIV is more often than not an STD. STD's make people feel dirty and ashamed.
HIV is I suppose one of the worse STDs. Maybe some cancer causing HPV's should be considered worse. Cause these days HIV can be quite manageable.
All these could cause anyone recently diagnosed to feel ashamed and dirty.
Plus whatever is in your individual psychological makeup about sex.
You can work out all the negativity over time so please don't go too far into this scenario of "my partner needs someone better than me." In a couple of months you probably won't feel that, things will be back to a normal feeling.
You seem to have some buy-in to stereotypes that generally people with HIV are promiscuous or that people with HIV are poor. I see you already reasoning your way out of the stereotypes, and the sooner the better.