Prolonged headaches/struggle to treat - suggestions?

Welcome ! So glad you're with us. Sounds like you've been on a major fact-finding mission to figure out how to best manage your migraine condition and what drives it. Good for you. Becoming aware of our triggers and symptoms is an important part of life with migraine. The process of trying new medications can be exhausting as we are (as you mentioned with nausea) often exposed to side effects that rival the very migraine symptoms we are trying to avoid. It's a tricky and challenging journey and you've clearly learned a lot along the way.
You mentioned that your doctor suggested that you see a neurologist? If so, I'm curious as the training of your current doctor because your treatment strategy as it is sounds pretty comprehensive. That said, we do generally recommend that people who have frequent migraine attacks be evaluated and treated by a migraine specialist. These doctors are generally neurologists who have extra training to navigate the complex neurological disease that is migraine. Finding these specialists can unfortunately be a challenge as there is a worldwide shortage. Still, worth a try.
Again, however, I'm impressed that your current regimen includes both prevention and rescue approaches. Good that you've had a CT scan and bloodwork. You are ahead of many people given these steps.
So, first, I'll say that unfortunately, having migraine is a lot about playing defense. As frustrating as it is, what you described regarding struggling to shake the attacks is fairly common. There are a few phases of migraine - prodrome and postdrome phases fall on either side of the attack itself and can oftentimes carry with them a load of complicated neurological symptoms:https://migraine.com/migraine-basics/migraine-phases. Add onto that the side effects of the medications and we often feel we are swimming in a muck of migraine - struggling to emerge before the next one hits. I also live with migraine (chronically) and remember when I received a clear brain scan, it resulted in my chronic migraine diagnosis. I remember feeling like it was a life sentence as there is no cure and the reality can be quite challenging. I'm not sure what I was hoping for - but definitely something curable. So, you are not at all alone in this feeling. To that end, we are so glad you have found and are with us. We are with you in this and here for you. It can really help to find a place where you can process, ask and answer questions, and receive compassion and support.
Second, as to your actual regimen, there are only a couple of suggestions I'd make for your consideration. One is to ask if you've done any thinking (and you likely already have) about your diet/lifestyle, etc. Again, I'm guessing you've already thought a lot about triggers- but it can help when we try elimination diets (including taking breaks from gluten, dairy, sugar, alcohol, caffeine, etc) to see if there is something we are exposing ourselves to without realizing it: https://migraine.com/blog/whats-elimination-diet-manage-one. I'm assuming you've already done some of this self-evaluation with the mention of the caffeine headache. Same thing about sleep hygiene, hydration, etc. Just do a bit of an assessment of yourself to ask whether or not there's anything you can shift that could make a difference.
Lastly, of the medications you listed as part of your treatment strategy, you did not mention any CGRPs or Botox. CGRPs are a newer line of treatment medications that are available in both prevention and rescue forms:https://migraine.com/cgrp-new-direction-migraine-treatment. A lot of folks are having success with these so it might be worth talking to your doctor about these options. Botox is a preventative strategy that has also proven helpful and can be coupled with other prevention and treatment medications: https://migraine.com/video/20-years-of-botox.
I hope this information and resources may prove helpful for you. As I said we are here to provide information and support anytime and are so glad you're here. Keep in touch to let us know how things are proceeding and what questions you have. Warmly- Holly -migraine.com team.

I feel your frustration. My brain CT and bloodwork came back clean as well. They can’t figure out why I get daily headaches and migraines. I’m allergic to the Imitrex family including maxalt and zomig. I found Pregablin (Lyrica) which is a preventative and has helped with the severity of the migraines. It is a controlled substance but not a narcotic. It’s made a big difference in the migraines and my fibromyalgia. 😀