Pregnancy weight gain making me upset

I have never been comfortable with my body and currently 32 weeks pregnant with 9kg weight gain. Doctor has asked me to slow down. I do not even eat any sugar stuff or even snack. Just mainly 3 meals a day and a guava as my mid day snack. My meals are protein based and low carb. I tracked my calories with an app and it shows I'm only consuming 1800 calories a day. I am also an active person that walks 10k steps a day along with 4× per week of strength training. I just don't know what to do to not gain so much. Any advice? I was also underweight at the start of this pregnancy. I'm 167cm and weighed 50kg