Sorry, i dont want to sound stubborn but i am still confused.
right now my understanding is that:

"нечто" is an indefinite pronoun (it means "something"). This is not the nominative or accusative form of "нечего".

so when i see a negation 'не' i will always attach 'чего'.
when i want to say 'there is nothing', i resort now to always use 'нечего'.

'нечему' is in dative form but i would rather use 'нечего' because of 'не', the negation.
'нечем' is in instrumental form but i would rather use 'нечего' because of 'не', the negation.
'не о чём' is in prepositional form but i would rather use 'нечего' because of 'не', the negation.

somehow my application and understanding is flawed.
please correct me.

help!