How to not gain more weight then need be

Jessica • Momma of a 3 year old boy, married to my best friend.
So I only use to eat one meal a day and since I found out I was pregnant I am now 7w1d and I usually eat two meals a day during the week and three on the weekend I'm sooo worried about gaining to much weight! I only want to gain the amount nessasary.. Any tips?!?