12 weeks and vomiting all the time

So I suffered with nausea at the beginning for a few weeks then it stopped I'm now 12 weeks and since yesterday after everything I eat I literally throw back up. I can't seem to hold anything down. Even fluids I'm struggling with. I don't feel ill just every time I eat or drink I'm sick. I've lost half a stone in 3 days which isn't good at all. Has this happened to anyone else?  Do you think I should contact my midwife?