I would just cut that in half for a week or so then take 7.5 upon waking in the morning for a few days. Then stop. You won't get to much of a withdrawl with that much that long. You might even just stop and see what happens.
The first time I tried to get clean I was using about the same as you.. 30 mg of oxy for about 1.5 to 2 months... my withdrawal consisted of aches and chills.. I was really cold and my body was shivering.. Your at a cross road.. your withdrawal isnt that bad.. the fact that the sweats havent developed yet saves you from the hot flases which is a GOD SENT.. you will still have trouble sleeping as I could barely sleep for a couple hours in this condition..
my best advice would be to stop now while you are ahead.. tough it out for a couple days and as grumpy said get some Immodium if you really really cannot stand the feeling.. you have no idea how many long term opiate addicts would love to be in your shoes right.. just quit now before your forced into longer term maitenance options like suboxone or methadone.. I know this is easier said than done.. but you just have to be strong.. and tough it out.