Stephanie, if I remember correctly (and I'm going back 30 years for this) just looking after 2 little ones all day, squeezing in a bit of work, and dealing with a chronic illness (in my case it was sarcoidosis, another immune disease) was more than enough to have me fly off the handle if anyone (usually DH) even thought about crossing me! Sometimes just seeing him coming through the door after he got to be out in the world all day and I was "stuck at home" was enough to set me off.
As has been said, you're really still in the post partum hormone flux period, plus you did have major surgery, no matter how much a Cesarean section is downplayed. Thyroid can be a real issue, because both pregnancy and SjS can cause thyroid disruption, and a few simple blood tests can determine that. You are facing many changes in your life, and your daughter is at the age now when her energy and activity levels sometimes seem endless, while yours are, at best, on hold.
Does DH understand SjS? It may help both of you for him to learn about the many varied aspects of dealing with chronic illness. Also, he may appreciate learning that probably one of the reasons he is the target of your temper, is simply that he's closest...not that you are angry with him in the biggest sense, but that he is the lucky person with whom you feel most comfortable and at ease, and he's also the most available emotionally to you.
By all means bring this "symptom" up to your doctor...it is a change in your usual condition, and merits medical consideration.