Did you look at ECIES?
No, but as I understand the wikipedia article, it seems a bit more complicated (or maybe it's just because I'm not comfortable with KDFs and HMACs)Can it be used with ECDSA private keys?
Yeah that's true it's really similar! Not being a crypto guy (even though I'm rather good at maths) I can't imagine I'm the only one who tried that kind of things, so why is it not used?
.Also, as I understand the article my implementation seems secure
I'm not a crypto expert, but if your implementation is truly the same as ElGamal, well it is being used. For example, Pretty Good Privacy implementations use ElGamal as one of the options.