"Do I have a small head?"
Translation:A bheil ceann beag orm?
Because you don’t really have anything in Gaelic but rather things are at you, with you, or on you, depending on the thing and what you mean.
Features of your body, physical and mental conditions, feelings are often rather on you than at you, so tha falt ruadh air he has red hair, tha an t-acras orm I am hungry, and a bheil ceann beag orm? do I have a small head?.
A bheil ceann beag agam? would rather mean something along the lines of do I have a small head among my possessions? (as in: somebody else’s severed head on a shelf in one of my closets).
It’s also sometimes used for features of inanimate objects too, eg. tha mullach feòir air an taigh the house has a grass roof.
As with everything, there are exceptions, eg. eyes are aig, not air: tha sùilean donna agam I have brown eyes, and those are not hard rules, so eg. tha balla aig an taigh seo (this house has a wall) here on Duolingo.
See Aig, air agus ann or The severed head on the Akerbeltz wiki.