Are these symptoms of allergies?

on Friday I started getting a sinus headache so I took a decongestant and it went away and the pressure started to come back later on. then on Saturday I woke up fatigued and lightheaded so I took a decongestant and nothing happened. then sunday I was feeling dizzy and congested in the head but no stuffy nose or sore throat or anything. and yesterday and today my head is still all blocked and congested and I have an overall not feeling well feeling. the symptoms pretty much stayed the same overr those days it didn't get any worse.