>be tranner
>do injections every sunday
>still get scared even though its been forever
>always have my boyfriend sit with me
>today
>hes comfy on the couch downstairs
>i tell him hes fine and i can be a big girl
>get everything prepped
>about to inject
>he comes up behind me with a bandaid ready
>awwww babe ^.^
>look down
>"diamonds"
>wtf...
>says its kinda hot i depend on him

why is he getting hard keeping me feminine?

Men like to feel needed by their woman for comfort and protection.
In that same vein (no pun intended) I'd get hard from a crying ex (who I'd still be attracted to) reaching out to me really needing me, girls begging me to let them cum, it's just submissiveness as a whole