I saw a dentist today and he said it looked like i was grinding my teeth when i sleep,could i have sleep apnea too? i have an infection in my mouth and he gave me an antibiotic, i think my headaches could be from that,will my headaches go away after?

Grinding teeth is not necessarily suggestive of sleep apnea that can coexist with grinding teeth otherwise. If your headaches are relatively recent it is possible they are due to the infection, otherwise any other condition, including possibly undiagnosed sleep apnea may contribute to your headaches as well.

Glad you're under Dentist's care. Antibiotic will help control infection until you can have tooth properly treated. Take exactly as directed until all are gone, and get in to see Dentist for Rx ASAP. Headaches can be caused/worsened by grinding, spreading dental infection, or totally unrelated other causes. Night Guard may be helpful. Posit your question to your Dentist.