Weight Gain... I'm worried

Elizabeth
Hey Everyone. 
I'm a bit worried about my weight gain.
I'm 10 weeks today but to date I've put on 6.5 kilos since before falling pregnant.
I have always had a really fast metabolism and had to eat 3000 calories a day to maintain my weight at 59 kilos which is underweight for my height.
I've gone from skinny to almost square looking and no definition around my torso at all and I'm worried I'm putting on too much.
I am eating a bit more than usual but only my evening meal. I also have horses so am excerising everyday with either mucking out or riding.
Am I worrying over nothing? 
Thank you everyone and sorry for the ramble x