I think I feel lymph nodes all the time but my doctor said no. What if he is wrong?

Not likely. Even if you think you have enlarged lymph nodes that your doctor says are no problem and he is wrong, as a general rule they are not likely to harm you, and with time if they are significant they will continue to enlarge, they will then be felt and dealt with diagnostically. The chances the doctor is wrong are low, but you always have the option to get a second opinion.