Weight Gain Before Conception?

Hi, I am new and not sure where to post this, so feel free to move it to another forum if it's more appropriate.

For most of my life, I have been either underweight or on the thin side of normal. Just before I went on the pill about 1 ½ years ago (for heavy periods and anaemia), I weighed 98 pounds, at that time, the most I had ever weighed in my life (i’m only 5 feet tall). Since being on the pill, my weight has increased to about 105 pounds. I’m 40 years old, by the way.

Recently, I saw a gynecologist about my husband’s and my plans to try for a baby. The gyn said that I should take folic acid for three months before trying to conceive.

So I went to a shop to get some folic acid, and saw some pregnancy vitamins which contain extra folic acid, plus additional vitamins and minerals that are supposed to be good for women pre-conception, during pregnancy, and while breast feeding. So I decided to get those and replace my regular daily multi-vitamins with the pregnancy ones.

Since taking the new pregnancy vitamins, I started to want to eat a lot, particulary craving veggies and whole wheat products. So I checked the label, and I saw that the pregnancy vitamins contain twice the vitamin b12 as regular vitamins. Vitamin b12 is an appetite stimulant.

So should I be submitting to my cravings because i’m desiring food that my body needs, and getting the extra nutrition now will make getting pregnant easier, or should I try to keep my weight down so I don’t start developing health problems because of being overweight. I’m concerned because my mother had gestational diabetes and toxaemia during her pregnancy, and I have a family history of heart disease and non-gestational diabetes.

I would appreciate any advice.