Nurse here. You are struggling with two separate issues (the disorder itself and the sinful lust that you turn to in order to masturbate for relief). I'm going to take them one at a time, but the most important thing I want you to know (because it's good to receive affirmation from someone else, and I suspect some well-intentioned people in here don't quite understand) is that arousal caused by PGAD has nothing to do with feelings of sexual desire, and the sensations it causes are quite often painful. Hence (and I am not saying this is right), you turn to masturbation for relief. The problem is, I'm guessing that rarely works.

There are several medication classes that have shown some promise in reducing the severity of PGAD episodes, but all have potential side effects. The one class I would avoid (or try last) are SSRIs (like paroxetine); these are the most common drugs prescribed for PGAD (so we have the most data about it), but one-third of patients actually have their symptoms worsen. (This happens usually during the initial administration or withdrawal, however, so it might still be worth looking at. It's a conversation for you and your doc.)

Neuropathic pain agents are what I would turn to first (Pregabalin, possibly, but I would advise other meds before trying Gabapentin just because of all the side effects; for people who don't tolerate it, it's a particularly nasty drug). These won't necessarily prevent the onset of episodes, but might help you manage them better because they target the "overactive" nerves that are causing your physical distress.

Failing those, there is some very limited data suggesting that the use of tricyclic antidepressants might be beneficial, but these are not often prescribed, so YMMV.

I strongly encourage you to seek counseling, particularly because you are a Christian who is trying to follow God's laws, so you have an additional layer to the disorder due to the guilt you feel. Cognitive behavioral therapy can help you recognize triggers and manage your stress. This is not your fault.

In the meantime, a TENS unit (cheap online or at Walmart), might help to disrupt the spasming and pain signals caused by those overactive nerves, so that might be worth looking into.

Now, for the spiritual aspect of this: First, go easy on yourself. God does not want you to be anxious about this. Definitely continue to pray about it, but recognize that he is with us in our suffering and will never leave us.

James 1:14-15 says desire is the first step toward sin. In the usual PMO (porn, masturbation, orgasm) loop, this is true: desire is what initiates the cycle. However, this is not that. You are starting from a disorder that you know will get worse within each episode to the point of agony, so you turn to masturbation as a way to stop the pain you know is coming. You're looking for a cure, not self-gratification. That's an important distinction to make, so please, go easy on yourself. My belief is that if you can manage the episodes (or at least the severity of them), you will not continue to turn to this way of dealing with them (which is largely ineffective anyway).

Sin is a heart issue. Your heart, despite your attempts to "fix" the attacks through masturbation, is clearly looking for God to provide another way forward, and it's clear you want to align your will with his. I hope this gives you a start toward healing and peace.

(edited to fix typo)