Braxton hicks @16wks???

Okay so I'm 16 weeks pregnant! This is my third baby but my children are much older 9 and 12. So I haven't been pregnant in almost a decade. Feeling a little bit of tightening at the top of uterus, no pain what so ever, maybe mild BH? Or maybe I'm feeling movement up there? I do have the stomach flu since yesterday. Vomited once have had some pretty bad diarrhea but it is slowing down. Drinking plenty of liquids including pedialyte and keeping all my liquids down and some bland solids. Coincidence that this is happening after stomach flu? No fear mongerinG please