Happy to answer you with my experience. I had been dealing with digestive issues and my doctor was treating me for that as well as fatigue as I have Hashimoto’s. I was feeling better and better. Then my symptoms returned. I had been following my doctors plan carefully, so she suspected I may have exposure to mold. But there are numerous symptoms to mold toxicity- runny nose, coughing, itchy eyes or skin, brain fog, lung infections, shortness of breath, dry skin.
My doctor asked me if we had had water leaks in our home and we had 3 known leaks and one unknown we were not aware of. We did not notice any smells or see any mold anywhere. So I was tested but she also said we needed to have our home tested. Otherwise treatment would not be successful because I would continue to be exposed to mold spores.
What you smell under the sink is highly likely mold.
If I were you, I’d find someplace else to live if possible. Since you are renting, the owner may not be agreeable to doing anything to have the trailer tested and then have the trailer cleaned up. It can be expensive depending on how much of the trailer has mold growing in it.
And I recommend you get tested for mold toxicity and for other reasons that may be causing your symptoms that have increased over the 3 years.
I hope this info helps. Take care.