A little over a week ago I started to notice a dark spot in the corner of my eye, like a dirt speck, that follows me in my peripheral vision. I notice it more when it's light (not necessarily against a white background, just when the room is well lit, especially if the light is shining in front of my eyes), and it's not so noticeable when my back is turned to the light source or the room is dark. It moves when my eyes move, but doesn't fall away when my eyes still like other floaters do. It also appears darker than my other floaters, but I can't put in the centre of my vision- always the peripheral. It is only in my right eye.

I've had a doctor look into it and she says it's not a retina problem and she cannot see a floater, so I am confused as to what it is. I am in my early 20s.

My questions are 1) based on my description, what would you say this dark spot is?
2) If it is a floater, is it normal for it to 'not fall away' when your eyes still? ie. it does not settle to the base of my vision if I stop my eyes from moving, but it darts with my eyes when they move
3) since this dark spot moves with my eyes, is it safe to say it is definitely an eye problem? it doesn't affect my vision per se - just annoying, and difficult to 'get used to' since it becomes noticeable when it's moving with my eyes. Is it safe to ignore in any case? It is likely to improve, or what can I do to help it?

Thank you very much! Sorry for the long post.