I keep getting canker sores once a month and am wondering would I see a dentist or doc?

Your choice.... Since you are young you may see a dentist more often, and therefore easier to get it when you have the sores. Treatment is not always too helpful, though. A visit is mostly helpful to make sure it isn't something of concern.
See your dentist. canker sore is the most common oral lesion. Individual ulcers typically last 1-2 weeks. Try to keep adequate oral hygiene as possible. If concerned, see your dentist for consultation. If your dentist has a diode laser in their office, this is another great option for treating canker sores immediately.
Canker sores. your dentist can help. Sometimes there is a hormonal component to canker sores. Other causes are stress, trauma, vitamin deficiencies. Your primary care can evaluate this. Some people are sensitive to SLS, sodium laryl sulfate which is in many toothpastes. Try using an SLS free toothpaste and see if this decreases your frequency of canker sores.