Help! How to cure gum disease and how long will it take for gums to heal?

I have gum disease. I have white healthy teeth but I have really bad gums. My gums are really sore and swollen, red, shiny and inflamed. The look all cut open and I feel like my gums are receding. It looks like my gums are getting shorter and my teeth are appearing longer and it really hurting me. Help! I don't know what to do. I really worried as I want my mouth to be healthy. How do I get rid of gum disease. I have already been dentist. I have took antibiotics and have had 2 dental cleanings. I brush my teeth twice a day for 5 mins and I was using listerine mouthwash but lately I've been using corosdyl. I never used to floss but lately I have started that so i'm following my dentists advice and been doing my best with oral care. It looked likes they were getting better for a little while but they are not really healing and don't look like they are improving much. They been like this now for 3 months. My dentist says I have gingivitis but I think I may have periodontal disease as my gums are really sore and not healing and my teeth are appearing longer. I been following dentist advice and it not working. i'm really worried. I also would like to get a smile makeover like veneers but I can't coz the condition of my gums and it not fair. I have really been trying to improve them. I have been to my dentist about 10 times over this. Any advice on how to get rid of it? And how long will it take to cure it? I'm really worried and I just really want my gums to be better.