Doxicycline is a drug that can accumulate in bile and tissues (liver, bones, spleen,,,) and is mostly
excreted in urine, you had an allergic reaction (vomitting) and for some reason may be your having sensitive reaction to sunlight because of it's accumulation, (usually not yellow but burn skin...., so it's strange too), it looks like excess of bilirubin in blood, did you test for direct and indirect bilirubin and for bile duct obstruction? and about bilirubin in urine???