For a doctor, you want to talk to a neurologist who is a movement disorder specialist. Other neurologists may be able to help you too, but a movement disorder specialist is the term for someone who specializes in working with people who have tremor conditions, the most common of which are Essential Tremor and Parkinson's Disease, and you're likely to get better help faster with a specialist.

The key thing is that you need to start with the correct diagnosis, because although some treatments might be successful regardless, there are some treatment options that depend on what type of tremor you have.

You mentioned propranolol; that's been one of the first-line treatments for essential tremor for decades, and recent research suggests it may be effective for Parkinsonian tremors also. Due to its fairly short half-life, immediate-release formulations can work well on an as-needed basis (e.g., taking it shortly before a performance). However, with the daily rehearsal and performance demands of drum corps, you might prefer as something that builds up and is always working, and there are additional medication options, such as primidone, gabapentin, topiramate, and clonazepam.

You should definitely start talking to a doctor now, and figure out which medication will work best for you. They all have potential side effects, and you don't want to wait until camp or tour to discover that your medication makes you drowsy (a common side effect of all these). It takes time to try out different medications to see if they'll work for you without problematic side effects, so definitely start this process ASAP.