17weeks and awful

I am 17 weeks pregnant with my third child and I am miserably sick all day every day. I don't know what to do. I can't do this any longer. I'm just too sick. I'm already on zofran which gives me headaches which I already suffer from daily and I'm constipated and nauseous and fed up. I don't know what to do. I can never do things with my kids and I always have to call into work or work sick and in retail that is awful. No one understands and I just am lost.