@kim45 Members in Connect aren’t able to diagnose medical conditons but we are able to use our personal experiences to share suggestions that have worked for us.
You mentioned not having insurance and hoping for a free clinic to evaluate your mouth. You could try an internet search for free dental clinics in your area. I used to work for a dental practice and we were involved in a free clinic sponsored by our county health system several times per year.
Generally oral cancer can start as sores or ulcers in the mouth that don’t heal. It sounds like yours come and go. There are condtions such as fungal/yeast infections, burning mouth syndrome and others which can cause similar burning in the mouth and spotty areas of sores on the tongue.

Here are a few things you might try at home for some relief until you get a firm diagnosis from a dentist. All of these can be found online for proper use instructions. But here is a small list of ideas.
~Warm salt water and/or baking soda water rinses

~Gently, brush the top your tongue several times daily to remove any yeast build up. The grey coating on your tongue may be an indication of yeast. By daily brushing you’ll reduce the excess yeast that may be causing the problem.
~Brush your teeth several times daily with toothpaste and floss nightly.
~Cut back on sugar, processed foods, soft drinks, juices, starchy junk foods, etc. Starch/Sugar can help yeast flourish. No alcoholic beverages.
~Eat probiotic foods such as non-sweetened Greek yogurt and fermented foods like kefir, mild kimchi. Here’s a good site for suggested foods. https://www.thecandidadiet.com/foods-to-eat/

~Nystatin oral thrush drops are available over the counter at drug stores. A pharmacist would also be a good person to ask.

These ideas may not cure your issue but they may help soothe your mouth. I know when I get a flare my entire mouth hurts even though there is only a small area involved. My doctor has prescribed · Clotrimazole Troches (lozenges) for me. I use 2 or 3 daily, letting them melt over my tongue for about 10-15 minutes. They don’t taste like anything but they do help to my mouth comfy again and they’re not expensive.
Let me know if any of these make a difference for you, ok?