My left ear started hurting really bad when blowing my nose today, and i feel congested and fatigued. could this be the start of a sinus infection?

Viral infection: Congestion, fatigue, runny nose- these are symptoms consistent with a viral upper respiratory tract infection. The left ear pain may be due to pressure building up in the middle ear because of blockage the tube that drains this region. I suggest you visit the pharmacy and ask them about over the counter decongestants and other supportive meds to relieve your discomfort.