Confused

So I have a daughter that’s 9 months old and my DH and I want to have our last child together while we are young. Anyways I have only had one period since I’ve had my daughter which was in November and it was only four days long. My period was suppose to start yesterday but it still hasn’t came. I took a test and it was BFN. I have been very nauseous the last week and if I don’t eat every 3-4 hours I get sick. Should I take another test or should I just wait?