Hi Emmahlee, welcome to the forum.
If you are seeing white dots, then it's likely not fin rot. One of the possibilities is Ich. Do the white dots look like salt being sprinkled all over his fins? How many dots do you see? For sure they are stuck to his fin, and not just some white particles in the water that just happened to land on his fin?
My lovely crowntail, had certain bits of his tail which have shortened
This may be due to fin rot or him chomping on his tail. Do you see the tips of these segments kinda beady, clumpy or melting or blackened?
Please try to answer the questionnaire below as detail as you can. You will likely not get a lot of responses at this time as I think most members in this forum is in the West, so it's night time for them now. I will try to help as much as I can, but I am about to leave my house though.....
What size is your tank?
What temperature is your tank?
Does your tank have a filter?
Does your tank have an air stone or other type of aeration?
Is your tank heated?
What tank mates does your betta fish live with?
What type of food do you feed your betta fish?
How often do you feed your betta fish?
How often do you perform a water change?
What percentage of the water do you change when you perform a water change?
What type of additives do you add to the water when you perform a water change?
Have you tested your water? If so, what are the following parameters?
Symptoms and Treatment
How has your betta fish's appearance changed?
How has your betta fish's behavior changed?
When did you start noticing the symptoms?
Have you started treating your fish? If so, how?
Does your fish have any history of being ill?
How old is your fish (approximately)?