well, if the doctors did not seem to worry that much, i'm pretty sure you were fine. this incident u had could have just been a result of all those things u mentioned happening at once: the dehydration, constipation, overweight, and pot-smoking. Just keep up with the doctor every once in a while to make sure things are going ok.
also, a similar situation happened with my cousin. and i don't think it sounded as bad as your situation, but it was still bad. his incident occurred because he had pot that was laced with something. so, who ever you got the pot from may not have been a reliable source. and it may not have been from the person who gave it to you, but the person who gave it that person, and so on.
just be VERY careful when you are dealing with drugs (you really shouldn't deal with drugs anyway). pot may not seem serious, and you can't really get an overdose from it, but you never know what might happen.
Well, dehydration can certainly cause a lot of those symptoms; the headaches, constipation, and even dizziness and nausea, so make sure you are drinking plenty of water. They ran blood work on you which is good. The low blood sugar you should watch. Many times diabetes can start with hypoglycemia (low blood sugar) and the extra weight can bring on diabetes sooner in your life. I'm not going to tell you you should lose weight because you already know that, but I do think you should be under a doctor's care and watch that blood sugar. If you can at least try and get a little exercise every day, that could do wonders. Even if it's just walking.
I'm wondering if you might have a circulation problem? You might want to ask the doctor about that. I'm saying that because you said your hands and feet get cold and numb. The body will pull blood from the extremities when it's not getting enough to the heart, lungs and major organs. The fact that it was your right arm that went numb and not your left is good because the signs of a heart attack would be the left arm going numb and chest pain. And I know you're young but even young people can have a heart attack. Your body is having to work harder because of the extra weight and that does put a strain on your heart, so if you can try to lose even a little weight that could help a lot. I know how hard it is. That's why I said to do all of this under a doctor's care. You need support. You're young so that's a plus on your side!
I would stay away from the pot and cigarettes as that can cause constriction on your blood vessels. Try and get plenty of sleep, drink plenty of water and try and eat as healthy as you can. Also get a little exercise every day and see if doing all of that will make you feel better. I think it will! I wish you well. Take care.