Ugh you described my first trimester exactly. I was so scared I was going to be admitted to hospital due to weight loss dehydration. I found the most helpful thing to manage the dehydration electrolyte popicles (I made them myself) and chicken broth. I also drank two ensure plus calories a day to give baby some nutrition. My stool was not formed at all (entirely liquid) and I just attributed it to morning sickness. I don't know if I had pouchitis but after one round of antibiotics- penicillin (for a UTI) I had ZERO relief of symptoms. I was diagnosed with hyperemesis gravidarum eventually and I did get relief at about 15 weeks (I still puke and have diarrhea here and there but my stool is formed and I've gained weight - and a belly!). Try the medication for morning sickness- it's not a miracle pill but hopefully it will get you to a place where you can start to manage your dehydration (for me this was HUGE to helping me feel okay). 

Also sending you so many good thoughts, I'm sorry it's so hard right now. 

ETA ne thing I learned from this process is you know your body well and if you feel you do need the antibiotics, from my perspective, you should take them 

Ashley, I hope you are doing better!!  I needed to be on antibiotics my entire pregnancy.  Fortunately, I was able to take Augmentin, but sounds like you are not.  Flagyl is not usually recommended in the first trimester, but I know for sure there are women who did low doses.  I don't know much about Xifaxan and pregnancies, but typically the nice thing about Xifaxan is that it is less systemic than other antibiotics.  It is however, Category C, based on studies with animals.  I hope you have found something that worked!!