I definitely think this is a pretty rare case if it is the Test Prop, but I would look at some other aspects of your life to see if it is anxiety, something in your diet or something else. Hopefully you can pin point what it is, or it just fades away. There are a few options if the insomnia lasts longer than you can handle. Like you said Tylenol PM, Benadryl, or most OTC sleep meds (almost all of them have the same active ingredient of diphenhydramine) can be an option, but I always prefer not to do the Tylenol PM or anything with acetaminophen in it if you don't need it. You can also try some more natural routes like Melatonin or a tea such as chamomile or valerian. Kava Kava tea has also been shown to help aid in sleep, but long term it can be hard on your liver and Kratom helps some people at the right dose/strain. Your last resort should be your benzos, barbiturates and prescription sleep meds like Ambien etc..If you do decide on the prescription route the try to limit it to a max of 4 weeks to reduce the risk or addiction.