Some of $A,B,C,D,$ and $E$ are truth tellers, and the others are liars. Truth tellers always tell the truth. Liars always lie. We know $A$ is a truth teller. According to below conversation,

$B: $ I'm a truth teller.

$C: $ $D$ is a truth teller.

$D: $ $B$ and $E$ are not both truth tellers.

$E: $ $A$ and $B$ are truth tellers.

How many truth tellers are there?

$ \textbf{(A)}\ 1
\qquad\textbf{(B)}\ 2
\qquad\textbf{(C)}\ 3
\qquad\textbf{(D)}\ 4
\qquad\textbf{(E)}\ \text{More information is needed}
$
1. We know that $A$ is a truth teller.
2. Let's analyze the statements made by $B, C, D,$ and $E$.

### Case 1: Assume $B$ is a truth teller.
- Since $B$ is a truth teller, $B$'s statement "I'm a truth teller" is true.
- $E$'s statement "A and B are truth tellers" must also be true because $E$ is a truth teller.
- Since $E$ is a truth teller, $D$'s statement "B and E are not both truth tellers" must be false because $D$ is a liar.
- Since $D$ is a liar, $C$'s statement "D is a truth teller" must be false, so $C$ is also a liar.

In this case, the truth tellers are $A, B,$ and $E$.

### Case 2: Assume $B$ is a liar.
- Since $B$ is a liar, $B$'s statement "I'm a truth teller" is false.
- $E$'s statement "A and B are truth tellers" must be false because $E$ is a liar.
- Since $E$ is a liar, $D$'s statement "B and E are not both truth tellers" must be true because $D$ is a truth teller.
- Since $D$ is a truth teller, $C$'s statement "D is a truth teller" must be true, so $C$ is also a truth teller.

In this case, the truth tellers are $A, C,$ and $D$.

### Conclusion:
In both cases, there are exactly 3 truth tellers.

The final answer is $\boxed{3}$