Advice

So I have ulcerative colitis and I stay dehydrate. Today I almost fainted. Tunnel vision, sweats, weakness. The works. I've never had this happen in my other pregnancies and although my on call doc said resting would help I feel bad. Very dizzy and drained. I would love some advice. Anyone ever have spells like that? They said if I end up fainting I need to be seen but honestly I just want to feel better.. Thanks in advace!