Vegetarian and loss of energy?

I have been a vegetarian for 2 years. recently i have been having loss of energy, especially when it is really hot out side. I never had these symptoms. My diet has been very unbalanced, but i have been a vegetarian for 2 years so i don't know why this is happening right now?I was think, that i might start eating meat again or try to balance my diet. I just don't know what the best solution is.