I didn't Know where to put this

Sorry if this doesn't belong in the right Topic. I just turned 19 over the summer so I'm not that young but lately I've been experiencing this weird sensation in my head and temple and it has me kind of scared. I just recently gotten over a Sinus infection and I was on amoxicillin which I had to continue to take I kind of stopped taking it as soon as I felt better but the doc said to keep taking it so I kind of delayed me taking it but lately I've been getting this weird kind of pulsating sensation. I'll get it and it'll go away or I'll go to sleep and be fine...but it's like as soon as I get it and there's nothing I can really do to shake it off. I do spend excessive time on the computer I thought maybe that's it? But I don't know. Anytime I go outside for a jog or a walk I feel GREAT but the minute I stay inside for a couple of hours doing nothing or at the computer I just feel horrible. I don't know if it's another sinus infection or what cause I kind of felt like this when I had that except it was more of like a migraine and eye pain. With this its just strictly my head and temple and it has me worried badly. I'm not used to being sick so maybe I'm just over-reacting but I don't know what I should do.