If you're having issues with your hunger response, it's almost certainly because you've simply eliminated meat from the meal, without replacing it with something nutritionally equal. Your hunger response is mediated by a number of food chemicals, which you've like never had to notice before because meat provides the appropriate ones automatically,

Solving it is easy - just eat protein (nuts, beans, etc) and fat (nuts, oil, peanut butter, etc.). That'll hit you with the right stuff to replace what you're losing with meat, and keep your stomach's brain happy because it's receiving the right chemicals.

People too often think vegetarianism is just a light salad at every meal. >_<