Question about SSI and SSDI?

I am receiving $404 a month SSI and $290 for SSDI. I have been told this is the max but I know people that have never worked a day in there life and get more. I had over 30 credit things because of working so that's where the $290 comes in. I have a minor child and was told that if he gets disability then my benefits would basically stay the same as I can only get a total of $674 a month. does this sound right or should I appeal something?