Why have I been feeling like this for almost 4 months?

Hi Everyone,
About 4 months ago I was due to go away for a couple of days and the day before I became overwhelmed with nausea, chills, aches, shivers and could barely keep my eyes open. I felt as though I needed to be violently ill but as I began to 'gag' nothing happened, no matter how long or hard I tried. I went away and continued to feel this way and panicky on top of this as I was afraid it would happen again, it left me with no appetite at all. I found myself needing to urinate more often so I made a Doctor's appointment for the day I was arriving home. She diagnosed me with a UTI, gave me some antibiotics and sent me for some blood tests. The blood tests came back clear, other than showing up the UTI. I still however felt sick and just not myself. So returned to the doctor who then prescribed me some anxiety tablets for 2 weeks, but because my head is and was so foggy, I can't remember how they made me feel in myself. Since then I have been getting headaches, my appetite is however a bit better now, I have lost a slight bit of weight (I'm putting that down to not having a great appetite for so long), I get sharp pains, twinges and spasms every now and then in my lower back, groin and lower abdomen. I have also noticed recently that if I put my hands out in front of me that I can't keep them still. I was also constipated for a while and still experience gurgling and swishing daily. I am absolutely terrified of being sick and I can no longer remember what it feels like to be 'normal'. Some days it is worse than others. I am so afraid that I have a cancer of some sort, but how quickly the ill came over me (a matter of hour) is what's making me think this could all be my mind going into overdrive. I feel like I need constant reassurance from a doctor and even when they tell me I'm okay I still don't believe them because I genuinely have no explanation as to why I feel like this.
Any comments would be highly appreciative as it is taking a horrible toll on my life.
Thank You.

Also, I am 20 y/o female and do not smoke or drink alcohol.