[ Pregnancy ] Open Question : just started 3rd trimester and...?

have a few questions: im due to go for glucose test what do i expect (i have been told to stop eating previous day from 8pm) Have to have another blood test at 28 weeks - what are these for now? I feel like my belly has stayed the same sized for 3 weeks now is this normal? - my baby is active and i feel her but i just dont see myself getting much bigger - just my back hurts alot