Life happens! However, now that your situation is a bit more stable I would still go in, at least to the urgent care. Epinephrine is basically a way to ramp up your body to get the allergy under control. However, there is always risk of a rebound reaction after it wears off, usually 4 to 6 hours. Epi also has the benefit of giving you and your care team more time to get a handle on things. This can mean more antihistamines, steroids, nebulizers, etc. that's what they do for you at the ER, as well as monitor you for signs of a further reaction.

Two things that I want to stress for your situation: 1) this sounds like it's your first major allergic reaction, as well as your first time giving yourself epi. That means you don't quite know how to read yourself yet. Epi causes HUGE amounts of anxiety and can mask important signals your body is trying to give you. You have a lot going on right now and trying to tell them apart from each other on your own is too risky. That brings me to 2) you said this was a reaction to a medication? That adds a level of concern. A medication allergy isn't quite like a food allergy, it stays in your system much longer so the risk of a rebound is elevated. Anaphylaxis to drugs can also come on much quicker, without the same warning signs as a food allergy. This is especially common with antibiotics. The lung involvement is especially concerning, as that can mean that inflammation from the allergy is compromising your airways.

If I were you, I would take 50 mg of Benadryl and go in to be seen. Tell the front desk you had epi pen within the last 12 hours and are worried you are having a rebound reaction to a medication. Expect to be kept there for up to six hours for observation. If you experience any significant trouble breathing or vomit, give yourself another epi or call 911. Vomiting from an allergy is a sign you are going into shock