Fentanyl has a very short half life so the wds (withdrawal symptoms) shouldn't last that long. I mean if you did what we call a Cold Turkey withdrawal. The worst of it should end in 10 days or less. And 5 months isn't really that long. It is long enough to become physically dependent, but it isn't so long compared to many of us here.
Is 12.5 mcg the smallest patch there is? I think so. If you can't just take off the patch and stay without it, I have a few ideas for you. I don't think even the average doc knows about this. The Mylan brand Fentanyl patch can be cut into a smaller size than it is made in. As far as I know you can only do this with the patch made by the Mylan company. The reason you can do this is because Mylan has found a way to fuse the Fentanyl to the glue on the molecular level. So when you look at a Mylan patch you can't see where the Fentanyl is because it's every where. The glue and the drug are one. Since this is so, I decided to try cutting one. Sure enough, no drug comes leaking out. I then applied it to my arm and it worked fine. I also found I could take a Mylan patch off and then put it on again and it still worked. So that's another trick you can use. Take the patch off for an hour and then put it on again until the wds stop. As the days go by try to keep it off a little longer everyday. Eventually you should have it off longer than on. And if you have also cut the Mylan patch down to a small size, you should then be able to stay without it. This would be like tapering off a pill. If your pharmacy doesn't carry the Mylan brand you may have to ask them to special order it for you and wait a few days. But its a very common brand and Mylan is a big well known co.
Benadryl will help you sleep. It can also dry up a runny nose and stop other flu like symptoms. If Benadryl isn't strong enough ask your doc for Phenergan. But that may dry you out too much. It's similar to Benadryl but stronger.
I have never tried this, but my doc claims Zofran stops many wds. I asked how much and he said 8 mg three times a day. So ask your doc about that.
I do know that Baclofen or Robaxin work on the shakes. One or the other. Clonidine is also used to lower blood pressure that usually goes up when you detox off an opiate. Clonidine also has a calming effect. Trazodone can be used to help sleep also, but it's habit forming so don't use it too long. Finally, one of the Benzos can help to calm you very well, but they are addicting, and must be used with extreme caution. But 0.5 mg of Xanax, Ativan or Klonopin once or twice a day does help. But don't use it longer than a week, and better to not use it daily, but only 3 or 4 times a week. Only until the wds are gone, or you will get hooked on it and then have to go through this again.
Remember, you can do this. You need to be determined and so long as you are you will succeed. I have done it twice and someday I may have to do it again. You also need moral and emotional support. If you have a friend who can sympathize, talk to that person often. Or come here and post often. Many of us here will give you plenty of support.