What the hell is wrong with me?..

So my SO and I have been TTC for 2 months, we aren't obsessed with testing but whenever there is a BFN we of course get really sad. However this month everything has been really intense, he's noticed that my moods are very up and down. One second I'll be happy then I'll get really upset, I have even bursted out crying for no apparent reason multiply times and my brothers girlfriend asked me if I was pregnant. We tested yesterday and we got a BFN and my period is due in about 4 days, I also had a craving for lays salt and black pepper chips on a tomato, cheese and ham sandwich even my SO found it a bit strange. I have not had morning sickness or anything so I'm not sure if I'm just going mental, some advice would help.