Seek a second opinion by all means. What a ridiculous doctor. Be sure the second doctor understands you have been taking the iron, so if you don't come up as having anemia he or she can tell why.
HATB, if you post the scan reports, I can tell you if there's anything worrying there. (If the nodes popped up suddenly, and then plateaued in size, that supports being not-cancer.)
But let's go ahead and presume that the scans show not-cancer ("reactive"). Then with digestive/mucosa involvement (loss of appetite, mouth sores, etc) we'd look for some infection that also creates enlarged nodes. E.g., are you of an age to have mono (Epstein-Barr virus)? Then maybe strep or Lyme. Etc.
If not infection, then next maybe some immune system problem, e.g. lupus. Do you have any family history of immune conditions? Ever have an ANA test for starters? Any odd personal immune medical history? Females of child bearing age are more likely.
We'd still have to explain the bruising, with normal platelet count. We'd therefor look at lowered coagulation proteins, which are made in the liver. Any liver tenderness? ALT and AST tests? Or maybe the GI problem creates a nutrient absorption problem, you need vitamin K to make coagulation proteins.
What you have is not simple. ERs or walkin clinics aren't good for such things.
No, you are not being ridiculous. This shouldn't be ignored.
But be aware that it's a TikTok trend for people to show up with imaginary diseases. That's not you, but docs are generally exposed to that trend these days. Still that doc seems strange, as Annie said.
The scans were the way to rule out node cancer; not your symptoms, not merely node size either. *But* your symptoms *are* important to find out what's really wrong with you. Absolutely, just as you say.