Vitamin B6/Unisom

I'm 13 weeks currently and I started taking this before bed around 10 weeks for my morning sickness and I have never felt better! Two days in a row I had forgotten to take it. The first day I felt off with headache. Yesterday I felt kinda sick, we went to the pool and cooked out and I had a headache all day, and on our way home we stopped and I had to throw up. (haven't been sick in any way since I started it) I took it last night and I feel great today.. With my first two pregnancies I was done with sickness by now. I was hoping I was sick because of being in the heat and now I'm worried I'll have to take it my whole pregnancy. I'm a bit disappointed and wonder if any of you ladies experienced this when stopping with nausea meds?