Hi, sorry for the late reply. I'm rather inactive really.
I think your portrait is great, I'm not lying or saying it to make you feel better. You do NOT suck.
You're right about the eyes being a little too big to be realistic, unless that was what you were going for. Also, some lines should be a little softer, if you don't mind me saying this. For example, the nose can be sharp, but the lines shouldn't be so solid. To mark boundaries and emphasize changes in shape, shading is used. But I think that your foundation is great; keep drawing!
Shading, especially with people, is really hard. Mine isn't really exceptional or anything, but something that helped me was practicing by sketching skulls. It sounds morbid and weird, but by learning the bone structure of the face, I also understood the protrusions of certain bones and where shadows would seem more natural. I don't know if I'm making any sense, so feel free to just ignore me, haha.
I'm glad you think my art is lovely!