It might be Chinese drywall.
Could be three things. The most probable is the pipe below the toilet (or sink or tub), it has a curve to hold water in there, to prevent sewer gas from coming back up the waste pipe, and it's gotten blocked. The curve in the pipe is called a "trap." If there is, say, a partial blockage of the trap or if some plumbing was done recently to those pipes and that curved pipe isn't done just right, then sewer gas is coming up into your house. The second cause could be the vent stack for that bathroom is not connected properly and so again sewer gas is escaping into your house via that pipe in the wall. Third thing is could be the hot water heater electrical heater gizmo needs replacing, if it corrodes, it can make the water smell like sulphur. Whichever item it is, your landlord really needs to call his plumber to check it out and fix it. In the meantime, you can try clearing the various drains or toilet in the usual ways (assuming you know how to... if not, just wait for the plumber).
I might add that you need to open the windows in your house, to let any possible gas out... sometimes enough gas can collect in a house to blow it up. If your landlord is slow about all this, by golly give him your notice and go live in an apartment complex for a while, even if you have to break the lease. If the fee to do that is high, take the landlord to small claims court, but make sure you have a couple friends go in the house the way it is now so they can back up your claim that the house stinks. You could also tell the landlord you're gonna call a plumber yourself, pay the bill, and then send it to the landlord and request refund... get the plumber to write down on the bill the cause of the odor. Again, if landlord won't pay, take him to small claims court.
By the way, the smell has nothing to do with your Hepatitis C, and so sorry you got that, but the last thing you need after going through all your treatments is a house that is making you sick, but might blow up, all because the landlord is trying to save money on a plumber. A stinky house MUST be fixed by the landlord, and if he beats around the bush, he's either a bum or outta cash to fix anything, in which case he shouldn't be in the landlord business. Gosh, I feel for you, keep us updated, if you are up to it.