Weight gain too fast?

I am 5ft 5" and had a pre pregnancy weight of 154 lbs. I am 24 weeks and have gained 21 lbs and I am now 175 lbs. Is this normal? I am worried. My shaped has not changed too much although bump is growing. I was weighed at 8 weeks of pregnancy by midwife and have not been weighed again. Please help a worried first time mum x