How to fix a floor that has fallen in (or who can I contact to get professional advice)?

We don't have the money to fix our floor and probably won't for a long while. Our bathroom floor has rotten and fallen in from underneath the tub and around the toilet. Underneath the house is only dirt and there's about 2 feet of space between the flooring and the ground. The toilet is also broken so that all that is flushed goes underneath the house and has caused a major infestation of sewage flies that we have tried everything to get rid of. We can't put in a new toilet until the floor is fixed and this one is unfixable. We have plywood holding up the toilet along with a cat tree and a few other things but it's shifting more and more all the time. The tub is held up with stacks of concrete blocks underneath but it is tilted to one side and the blocks are sinking into the mud from where the toilet water has gotten under there. We thought we could save up a little of money at a time and buy small pieces of what we need to fix it, which will take a while,but it's our only option.

So all that aside, what would it take to get this fixed? We know it's gotten way out of hand, and that we'll have to tear out the floor and start over, but we've had a lot of stuff happen the past could of years that have gotten in the way of fixing it. ( don't say anything about us waiting too long, we know that and we couldn't help it, I don't have time for less than helpful comments)

Please help us, we would rather not let this house go to the point where it would be condemned. Thank you!