Need to get rid of a huge, under the skin, painful zit!?

I actually have two at the moment (which is very frustrating because I went on birth control to get rid of my painful acne break outs), but the newest one is the reddest and most painful. I would like for it to go away as fast as possible! I already washed my face with acne wash, put astringent on the zit, and put some benzoyl peroxide cream on it. I have done this for every other zit I have, and it does not help to reduce the size and pain by morning. So, here are some questions! :What else can I do? I heard toothpaste works, but I only have the whitening kind. Can I use that? And I have a clay mask with avocado in it. Should I put that on the zit overnight? And, what can I do to help prevent these painful, annoying, mega red under the skin zits that sometimes take a MONTH to go away?!?! Thanks so much!