Doc says I have CFS but it has only been 4 weeks!

I'm a 20 year old female college student. I have medium to heavy school and extracurricular load and have been a fairly active individual.

I have been diagnosed by with Peptic Ulcer that has been occurring for the past couple of months, then since 4 weeks ago I started feeling irregular chest pains, back pains, muscle pain (on shoulders, legs and arms), pins and needles kind of numbness on fingers and legs, debilitating fatigue after some work that is sort of relieved by naps but not completely, shortness of breath (climbing stairs and walking long stretches are a challenge), occasional dizziness, lack of concentration and sometimes poor memory. It's hard to sit still and focus. I also have anxiety attacks about petty things, though I've always had a calm and cool personality.

I don't know if this has something to do with anything but I also noticed that whenever I'm in class taking notes, I have the correct spelling of some words in my mind but I write them down wrongly. Of course this happens to every one once in a while but it has been oddly happening more often to me now. I don't have trouble sleeping just body pain when I wake up. At the end of each average-activity day, there's also too much tiredness unlike before. All these symptoms are fairly recent unlike my persistent duodenal ulcer attacks.

My sisters guessed anemia but my RGB count is not significantly low. It's low but not enough to cause these symptoms and to officially pass as anemia.

I saw two doctors already. Doctor A said it's stress related or psychosomatic, but really I'm the least stressed among my colleagues and I've a good disposition and I manage time and activities better than most people I know. I'm also thinking, all these just because of stress? It's hard to accept. Then doctor B, a gastrointestinal specialist who diagnosed my peptic ulcer, also passed it as stress and/or CFS when I consulted him lately. I also had my CBC taken, with slightly low hematocrit and hemoglobin levels beyond normal count (but not low enough for anemia) and also slightly low WBC count even though I don't have apparent viral infection. I have slightly high seg count and low leukocyte count, both also not on the "normal" range. Though when Doctor B saw the CBC, he wondered why I had low WBC but didn't really consider it in his assuming CFS.

Help! Should I settle for that diagnosis or consider hyperthyroidism etc instead?

P.S. Some parts of my neck are tender. I don't know why. Maybe I'm a hypochondriac? 'Cause I'm aware it might suggest thyroid disease.