I really understand what you're passing through, I've lived the same and even worse. I was expulsing dozens and dozens of worms daily, but stool samples always came back negative, even when worms were clearly noticeable. They even sent me to the psych ward because I was losing weight so fast and they couldnt explain why.
Here is what I suggest you do. First, forget getting help for a standard doctor. They just won't help.
Second, you must know that parasites are usually present in every human body, but will cause problems only if they're not kept in check by the immune system and the friendly flora.
To my opinion, one of the best anti- parasite herb is Black-Walnut . Try to put your hands on a really strong Black-Walnut tincture (Most on the market are too weak. The Hulda Clark website sells a good one). Also start making and drinking kefir, to reintroduce healthy bacteria into your gut asap, as the Black-Walnut will likely kill some of them. Kefir has also the advantage of directly fighting the parasites, which most probiotics wont do. Water or milk kefir, or both is even better.
Last thing, you really want to look into your diet. A healthy digestive system (enough stomach acid for example) will not allow parasites to survive. Therefore, you must eat as healthy as possible, and easy-to-digest foods. If you eat animal proteins daily, I suggest you supplement with HCL tablets, or drink apple cider vinegar with every meal.