Keflex Dizzy Spells, Couple Days, Antibiotic, Stomach, Sleep

i was prescribed keflex 500mg to take 4 times a day yesterday in the er for a infection in my tooth which is being removed in 2weeks. after picking them up today, i've took 2 doses so far. Im happy my tooth for the first time in 3months is not throbbing, but i have been nauseous ever since the first dose, and have vomited 2 times, both about a hour half after taking them. I found that after moving about (lite cleaning, just walking around) i get dizzy spells and have to sit down.. Haven't had much sleep in the last couple days and cant seem to get to sleep because of my stomach being so upset. Seems this is normal with this antibiotic,but if ot gets worst i think im going to stop taking it.