Given wrong student loan account

Hey, so basically I applied for my student loan back in May but I didn’t put my household income down. I sent off the PF2 form in September and finally got the confirmation I would receive it today 13/10 after weeks of calling for any updates. However I’ve been awarded a very low amount, my brother is receiving 9k and I’m only getting 6k. I check my bank account and only received 2.1k??? I have a disability and have received DSE, and studying in London. Is that the reason? I have rent to pay and it doesn’t even cover that. I received another email saying I may be entitled to additional maintenance loan and I need to send any benefits I’ll receive whilst studying. However I’m confused because I don’t have any, unless they are talking about household inwhich I have a younger sibling with a chronic condition so she receives PIP. The only thing I get is DSE from SFE. I need to get this sorted ASAP

ALSO, with my DSE. Am I entitled to extra money on-top of my original loan?

Thank you