You don’t say how long it’s been but it’s completely normal to feel a sense of disconnection both sexually and emotionally after a relationship break up.
Denial is a wonderful kink, and the experience when it’s being imposed by someone else is often even more powerful, so the fact you’re struggling doing it by yourself is nothing to worry about.
Orgasm denial is actually a very different animal when you do it to yourself, in fact in many ways it’s the reverse of the experience. When you’re with someone it’s about the loss of your control to them, and being under their power. When you do it by yourself it’s ALL about self control, about the challenge of stopping before you go over, of riding the edge without release. It’s a big switch and takes time to get used to and enjoy (and it may be you never find it enjoyable by yourself, that’s okay!).
I’d suggest you take a break for a few days at least, in one of two ways. Either just avoid worrying about edging and do what you want and enjoy the freedom of cumming, or not!. Or if you feel like more of a challenge, try three or four days of ‘no touch’ where you see if you can handle not playing at all, but still maybe read through Tumblr, read some erotica etc. to make it more intense.