OK, here's a short (HA-HA!! ) review of the basics....
There are two basic types of migraines. A "Classic" migraine comes with the "AURA", which are usually visual disturbances which are a warning that a migraine is beginning. When you notice the aura symptoms, that is the time to take medication, known as an "Abortive" drug (like Imitrex). This should stop the migraine attack in its tracks. If one medication doesn't work, there are a wide variety of meds that can be tried.
A "Common" migraine is the same painful headache, but doesn't provide you the "Aura" early warning system.
The "prodrome" is the set of symptoms you feel prior to the excruciating pain setting in. I personally have common migraines, the biggest "trigger" I have is a change in weather, either barometric pressure or temperature. A good way to figure out your own triggers is to keep a diary of all food and beverages you consume, and what your environmental factors are present. You keep this diary going until you start to see the patterns of foods or other similar situations that always end in a migraine coming on.
Other than food and environmental triggers, hormones (or PMS), loud noises, bright lights, even eye strain can be triggers.
I would suggest seeing a Neurologist as soon as possible. It doesn't sound like the doctor you have been seeing is knowlegable enough about migraines to treat you correctly. I've had migraines for 34yrs, since I was 8, so I've pretty much learned all the ins and outs of migraines. In all that time, I've never heard of a "silent" migraine, so I have no idea where you got that term. Also, your doctor should not have just prescribed the Imitrex for you. The first time you try it, it should be given via injection in a doctor's presence, because the side effects can be dangerous. Personally, I would rather have the migraine than to take Imitrex, which gives me horrible side effects. Plus, it doesn't do anything for my migraine.
The critical issue here is that you don't take more medication for your migraine attack than prescribed, or more often than prescribed. You should not take pain medication, prescribed or Over-the-Counter (OTC), more than two days a week. If you don't observe this limitation, you can (and probably will) get yourself into a cycle of "Rebound" headaches. Rebound headaches are horrible and once you are in the cycle, you must force yourself not to take any pain medication at all until your system clears out.
If you are getting migraine attacks frequently, like once a week, you should get a "Preventative" medication prescribed for you. There are several different kinds of preventatives, so it may take some time to find what works for you.
You should also have an "Emergency" pain medication to take if your abortive medication doesn't work. Some people have to get a pain injection from their doctor or from the local Emergency Room.
Most migraine sufferers find the right combination of medications over time. The faster you get started with a Neurologist, the better off you are going to be.
Lastly, I totally get the depression end of getting migraines and not knowing the answers. I am still fighting the frequency of my migraines, and am actually on SS Disability, partially because of my migraines leaving me unable to hold any employment. I have other medical problems too, so the depression actually has to be medicated too.
Anyway, I hope I gave you some good information, at least a decent overview of migraines, and I hope I answered some of your questions. Let us know how you are doing.
"The weather is here, I wish you were beautiful."
- Jimmy Buffett