High-Risk Pregnancy and Yom Kippur Fast

I am currently in my seventh week of pregnancy. I am considered a high-risk pregnancy because I had a miscarriage two months ago (thank God, I conceived again just a few weeks after that), and in addition, in both previous pregnancies, I was also considered high-risk. In the first pregnancy, I had to undergo 2 surgeries to preserve the fetus, and in the second pregnancy, also a surgery to preserve the fetus. In both pregnancies, I delivered prematurely, and the baby in the second pregnancy required intensive care in the NICU for some time. In the current pregnancy, I am supposed to undergo surgery in about 3 weeks. Additionally, in this pregnancy, I have a very increased appetite on some days, and when I do not eat/drink, I experience severe stomach and head pains. Should I fast on Yom Kippur? If not, how should I conduct myself during the fast? Thank you very much and have a good and blessed year.

Shalom and blessings 

You should drink in measured amounts.

I am attaching the instructions for drinking in measured amounts:

A. The amount of drinking less than a full mouthful is 40 ml. Even on Yom Kippur, it is permissible to measure the drink to know if it is less than the amount [at the rabbi's house, you can get 40 ml portions]. 
B. Since, as mentioned, you need to drink less than the amount, you need to pause between drinking and drinking for the time "to eat a piece," which is 9 minutes for stringency. Therefore, do as follows: drink less than the amount [i.e., 40 ml], wait 9 minutes, and then you can drink another portion less than the amount, and so on. A patient who, according to the rabbi's instruction, needs to wait less than this time between drinks, can reduce
the waiting time to 4 minutes, and if necessary, reduce to 2 minutes, and if there is a great need, drink the required amount in several sips [but not in one gulp].
C. A patient who is allowed to drink does not have to drink only water, but can also drink sweet drinks [and sometimes it is even advisable to drink sweet drinks, as they strengthen more and you can drink less].
D. Any patient who needs to eat or drink should consult with a doctor about the amount of food or drink needed for the whole day, and divide it into portions, but should not eat or drink more than necessary [most patients in danger suffice with drinking in portions of a liter of liquids, and there are patients who need a liter and a half of liquids, but usually there is no need for food, so they are forbidden to eat, even in portions].
E. Example of dividing the drink into portions: a patient who needs to drink three liters of liquids a day can divide the drink as follows - after the fast, drink a liter and a half, and the remaining liter and a half drink in portions during Yom Kippur. And according to what has been explained, that you can drink 40 ml every ten minutes, it turns out that you can drink about a quarter of a liter in an hour, and in two hours - half a liter, and in four
hours - a liter. Thus, he will divide the required amount throughout the day. 
In any case - a person who feels that he is about to faint, such as seeing black before his eyes or experiencing severe dizziness, or feeling weakness that makes it difficult for him to get out of bed, should drink in portions. After he has strengthened, it depends on his condition.