Bed size

I was wondering what size is normal for a married couple with a 4 year old who sometimes comes in during the middle of the night and a baby on the way. My husband and I have a full and it just is not big enough with my growing belly and our 4 year old coming in when he wets his bed. My husband is instant upon it being big enough we just need a new one because of a lump but a full is big enough and I'm disagreeing. Any thoughts or suggestions??