Changes in Belly Size

I know that a normal belly increases as the day goes on, but mine seems to be all different sizes during different times of the day.

When I wake, it’s hardly there but close to bed time, it appears as though I am due to give birth. I'll admit that since being unemployed I'm not eating as much as I'm not in any routine - i.e. breakfast/lunch etc - but I sometimes feel like its just belly fat and not a baby.

I'm 15+2 and I have put on a stone, yet I can still fit into my jeans...