You also need to make sure that you're pulling with your back muscles, rather than your shoulders/arms.
I came down with tendonitis (tennis elbow) around Christmas. As with JRY309 above, I had to lay off shooting for about a month, and I now wear braces on both elbows. I CONCENTRATED for the first few weeks, with a 45# bow, using back tension when I draw. Now, shooting bows is part of my therapy, as my elbows feel BETTER after a shooting session. I DO notice that I have a spot between my shoulders that feels "tired" after a long session with 60# bows...which tells me I'm using the correct muscles....
See the DOCTOR....and good luck!
Kevin