Could this be an infectious diesease?

You should see a doctor, sounds like you have some crossover symptoms of a few things, but hopefully nothing as serious as HIV. It's possible you are suffering a migraine or migraine aura which can cause your body to do a lot of really strange things like the pin prick sensations, tinnitus, light/sound/smell sensitivity, balance problems, concentration problems, and sometimes stomach upsets go along with that. The rash is a concern, too, make sure that's not an allergic reaction. Good luck, hope you find a good doc who can sort it out quickly.