International student single mother of British Born Child

[wahi66]

Hello Helpers

Can anyone please help with this case.
I am a single mother of a British child who holds british passport is on International student visa and wants her visa to be replaced as mother of british child. the father of the child is married to another woman. The child is living with me all the time. The father also see the child mostly regularly but the up bringing is under my arms. I am also working part time on student visa.

What options i have? and
what type of form i would have to use?? and
what evidence i need to provide??
is there any form who deals this kind of applications where i can find more info??