First, I think it is important to be consistent with your meds, so that they work for you optimally.
I agree that maybe you should speak with a psychiatrist, because you are worrying very much (having loads of anxiety-related to your children).
Kids need to be kids... and the one who's allergic, I would definitely make sure he/she always has an Epi Pen ...and tell any of the friends parents about his allergies, so that he/she can go to friends homes.
You older son, it could be anything, from something he ate to something he did ...a bruise of some sort.
You mentioned that your children are beginning to follow in your footsteps. Perhaps they see how you react and think that is how they should react? Kids are quite observant as you probably have noticed.
Try to be more consistent with your meds...for your sake and piece of mind. You'll feel better when you have a steady stream of meds instead of sporadically taking them, which can mess things up chemically.