Is it normal for nausea to come and go from day to day in early pregnancy?

Morning sickness usually occurs because of high hormones and empty stomach which allows acid to build up in you stomach. For a week I took pep-to tabs for my heartburn and my sickness vanished (but of course it's also for nausea). I stopped and I was sick again. Now at 12 wks some morning I wake up feeling perfectly fine and others day I feel like I'm going to throw up my liver. ugh. True enough though, some people get over sickness faster than others. My sick was sick one day for both of her pregnancies but my first pregnancy I threw up so much I lost 15 and was so dehydrated that I couldn't stand without falling back down. Luckily with this pregnancy I can actually eat!!!