Experiencing Knee Pain, Headache, Anxiety. No Relief From Medicine. Have Low Vitamin D. Prognosis?

Question : Over the last few months I have been having weird symptoms. It all started with knee pain. I only seemed to get it when I was standing for a long period of time. Mind you I am only 19. I am a male. I am not obese, but I have a gut. Anyway, after one night when my knees hurt particularly bad I went to the E.R. and they took x-rays and said there was nothing. I took joint supplements and nothing improved. In fact, my elbows and ankles began to hurt from time to time as well. I also got headaches that only lasted for a minute or so. Also, one night I felt very hot in the face and my neck hurt quite badly. I decided to see a doctor and he took blood for testing. he said he tested for RA, kidney function, and liver function and everything looked fine. I had low vitamin D, so he started me on 50,000 IUs once a week for 8 weeks. As of yesterday I am on week 6 of my treatment and nothing feels drastically better. In fact my knees felt better for a little while, but now they hurt just as bad as before. Yesterday while walking around a city with my friend, I noticed a bruise-like feeling in my lower abdomen. It hurt, but not too bad. I checked it out last night and saw nothing. This morning I checked it out as well and I also saw nothing. About an hour ago I checked it out again and it has a speckled blueish purple bruise like pattern over it. I didn't get hit there or anything. What could this be? I also get a strange slight burning in my shins and fore arms from time to time. My shins have lost some muscle mass over the past few months and when I do simple exercise like throwing a football for an hour or so, I get sore for at least 3 or 4 days in multiple quadrants of my body. My lymph nodes have seemingly gotten swollen a few times over the last couple of months as well. I also have a very lump texture under my skin on my abdomen, upper arms, and next to my shoulders. I have also recently noticed a bump on my XXXXXXX the size of a pencil eraser. Please help me out. I have no medical insurance and I work two jobs, so I need to know if I need another doctors appointment soon or not. I am also experiencing quite some anxiety at the moment too. THANK YOU!!!