Tealboy;
I also suffered from a bout of tennis elbow a few years ago. And yes it was very painful to shoot my bow, I had it in my bow arm.
Are you sure it is the bow that is causing it?
I originally thought maybe it was my NEW bow that was causing it, but then between the doctor and my self we figured it was something else, I had a pizza Franchise and I was making and hand rolling huge amounts of pizza dough everyday , this was the source of my injury. The doctor prescribed a type of elbow strap that is worn on the forearm just below the elbow and it has air filled pockets on it , and he prescribed anti inflamitory medication, and to try and disscontinue the activity that was causing the problem, REST THE ARM.
Now if you still think it is shooting your bow that is the source of your injury then take a look at your form. Is it your release arm or your bow arm that is in pain?
If you are shooting with a tensed arm try shooting with a relaxed arm, if the shoulder and elbow are not relaxed when shooting your shots may not be the only thing that suffers. Do you shoot straight elbowed or a slightly bent elbow, I find a slightly bent bow arm elbow is a more relaxed arm and causes me to torque the shot less. Make sure that you are also shooting with a relaxed bow hand, a tense hand will like to torque the bow also.
I also decreased the amount of shots I was shooting when in pain, I TRADED QUANITY SHOTS FOR QUALITY SHOTS[8D], Shoot every shot as if it is the only shot that you will get, make those shots count, I found once I was getting tired and in pain my form was going down hill and that meant it was time to stop shooting, and come back later or the next day and shoot again.
You say its getting pretty bad, then I would say have a sports medicine doctor look at your elbow, better safe than sorry.
I hope it gets better soon for you

" GOLDEN KEY FUTURA STAFF SHOOTER "
Deborah KF