I did not answer the poll because it depends on how you were taking the pills. 150 tabs of 10/325 prescribed every 30 days equates to 5 pills a day. 100 tabs of 10/325 prescribed every 30 days equates to ~3 pills a day.
If when prescribed 150 pills a day, you were taking as a baseline (meaning most days) 3 pills a day and only taking 4 or 5 on bad days (e.g., once or twice a week), then the reduction should not have been a major problem except for on bad days when you need more than 3 but are no longer allowed more. If you were taking 5 pills a day every day, then the reduction from 150 to 100 pills is significant as you were taking 50 mg of hydrocodone a day and now you are taking 30 mg of hydrocodone, which is a 20 mg reduction in hydrocodone. That is quite a steep drop when comparing to the reduction amounts typically used to taper off of a medication. So it is likely your symptoms are due to withdrawal from the hydrocodone.
When you reduce a medication that was controlling your pain, most times the pain increases as you aren't taking the amount required to control your pain anymore. Pain also increases as a symptom of withdrawal, so it will take more time at the lower dose to truly know what your real pain level is.
The better approach would have been
(for example) to reduce the amount by 1/2 pill per day each week to see where the pain began to break through. This would have more better isolated the true pain from pain due to withdrawal and it would have allowed you to determine how much medicine you truly believed you needed. But, if you only took the hydrocodone when you had pain and not on a schedule and you needed to take 5 a day, then you probably truly needed 5 a day. If you were taking hydrocodone on a schedule regardless of if you had pain or not (e.g., every 4 hours), then a slight reduction;
for example, 1/2 pill per day for a week and the another 1/2 pill reduction per day for a week, etc., would have been a better approach of determining how much hydrocodone was truly needed to manage your pain. In other words, the hydrocodone was dropped from 150 pills to 100 pills without any medical evidence showing that was the true amount you needed to manage your pain.
Be sure to always discuss a realistic tapering schedule (like the example I have written) with your doctor first to make sure that you both agree that the schedule should be used for determination of your true pain level.