You should be fine to take an Advil PM, I'm assuming your taking it for the sedating effects of the diphenhydramine..?
What you really need to deal with is your panic attack. A panic attack is just your flight or fight response and the physical symptoms are your body preparing to 'fight or flight' - hence your heart beats faster to pump more oxygen into your muscles, you breath faster etc. It becomes problematic when there isn't actually anything to fight or run away from, so the adrenaline you've produced does not get used up, and sits in your system making you much more anxious than usual. Adrenaline takes 10 days to be eliminated from your body. The best thing way to speed up this process is to burn off that adrenaline through exercise.
Also, the good thing about panic attacks is that they are very very manageable. Work on your breathing (do this all the time at first so it becomes a habit), slowing your breaths down so it's 3 seconds in, 3 seconds out. Breath from your tummy, not your chest. Breathing through your chest will give you chest pains and just contribute to anxiety when you think that means you're having a heart attack. The hardest thing about panic attacks in convincing yourself that that's all they are, and that they're absolutely harmless.
It's important to deal with your anxiety symptoms now because they'll feed on themselves - the more scared you are of having another panic attack, the more likely it is you'll have another one, because you're anxiety is being kept at a high level. I had my first panic attack off a dose of mushies and it turned into a full blown panic disorder. Like you I was scared to take anything (even to the point I'd trip out someone had replaced the mushrooms on my pizza with magic mushies). Now I've dealt with my anxiety and I'm much more in control of it than ever before.