I have a three year old daughter who I breast fed until she self weened at 9 months old.
My advice for you? Stop nigt feeding your 13 month old. Starting at nine months of age babies no longer need to have night time feedings. Your son is waking up out of habit and because he wants your company.
The problem with continuing night feeding is not only does it make you tired, waking up at night makes your son incredibly overtired. At this age he should be able to fall back to sleep naturally on his own if he wakes up.
There is a book I read when my daughter was a baby that dramatically changed my life. It has taught me how to let her get the sleep she needs. She has an early bedtime at 6:30 and wakes up at 6:30 in the moring. She never tantrums and has very productive days with a great attention span. The name of the book is:
"Healthy Sleep Habits, Happy Child" by Marc Weissbluth, M.D.
I also have a three month old son and have starting using the advice for infants in the book and it is going great!
If you quit the nightime feedings you can probably keep up the day feedings until you son decides to ween himself because both of you will be better rested. J.