Feeling sick and lethargic just before bed everynight...

My midwife doesn't think it is a problem. I think it is horrible it is like i have to puke but havent puked just feeling really nauseous everynight about 3-4hours before i go to bed. It can't be food poisoning or anything and i got over my morning sickness months ago. I am 26weeks. Is anyone else feeling like this or have they? There doesnt seem to be anything causing it but i am so over it.