Hello, It Is Currently 11pm EST And I Have Been

Hello, it is currently 11pm EST and I have been feeling quite ill all day. It started early this morning around 4am, woke up extremely nauseas, and have been since, no cramping, no other symptoms. Tried to use the bathroom, it was less than satisfactory. No vomiting, no diarrhea, infact, I am actually constipated? How is this possible? Also I've had a headache on and off all day, and an overall feeling of illness in general, malaise, if you will. PLEASE HELP, my symptoms leave me with little to no answers since they are so general :( I just want a better idea of what this could be? (I suffer from peanut allergies, but I am very careful about it. I ate some sausage that may not have been kept at the proper temperature last night. And as of recently cut out wheat from my diet as I found hives forming on my body after consumption a few days in a row, and kept track of my food intake.) Thank you for your time.