Sickness went away but now its back..

Am i the only one that has experienced nausea and vomiting that was going strong then went away for a week and now its back? I had bad nausea and morning sickness all day every day for the first 12 weeks, then it went away for about 4 days and i thought i was off the hook then BAM! Its back with a vengeance. Im 13 weeks today and cant even get out of bed im so sick.