I'm sure this has been asked... but I need some help.
I live in a 2 story townhouse. My bedroom is upstairs and there is a bathroom off the bedroom. About a week ago, I started noticing a smell. The smell comes and goes. Sometimes it's so bad I can't go into the bedroom and 45 minutes laterI can't smell it at all. This is not a bathroom that is regulary used (at least not the shower and the downstairs 1/2 bath is the one that is mostlhy used for restroom purposes). As of tonight, I've just shut the door because the smell is so terrible. It's so bad at times that it concerns me that it could make my son (or even myself) sick.

At first, I thought it was a dead rat... and I haven't ruled "anything" out. I have poured a bottle of draino down the garden tub (and flushed with hot "tap" water). Is there something I can do to test or pinpoint where the smell is coming from.. and what can I do? Also, I hate to be plumbing stupid but anything that you can do the "dumby" down the answer would be helpful, since I don't know the plumbing lingo/terminology.

Please help... I am a single mom and needless to say money is tight (since it's almost Christmas) and I need to try to "attempt" to resolve this myself (if at all possible). I'm pretty handy about working on things myself but plumbing (or dead rodents) is not my niche... This is my first post.. hope I haven't been too lengthy... Thanks to anyone for suggestions