I Have Been Sick On And Off For 3 Weeks.

I have been sick on and off for 3 weeks. I was thinking I had a stomach virus that would not go totally away. I get really fatigued, weak, nauseous, get diarrhea, and even if I'm hungry and eati immediacy feel sick and like throwing up (even though I haven't). Yesterday I was having another bought of the symptoms above, but also a new symptom. My stool had turned yellow and attuned lookalike foam. Also, black specs that look like coffee grounds are present.
Any ideas?
Thanks!