Only 5 weeks and so sick!

Marie
I'm 5 weeks pregnant and feel so sick. I'm nauseous but not vomiting, weak, tired and have a constant headache. I'm also having hot and cold flushes, is it normal to be so sick so early? 
I have a toddler as well and had bad sickness but I don't remember it being so early or constant last time. 
Thanks :)