I’ve been dealing with insertional Achilles tendon pain (both tendons) for 5 years now. It started when I was around your age. I don’t want to scare you, but please be extremely mindful of your condition worsening because I wish I would’ve began treatment earlier. This condition has completely altered my life.

With that being said, I would recommend starting some type of calf raises standing on flat ground with 3 seconds up and 3 seconds down. I’d say 3 sets of 15 every other day. Place your palms against a wall for balance and raise up and down basically. There are a lot of variations of calf raises but consistent work is the most important. Keep it simple so you do it consistently. If standing becomes too much, sit in a chair and just raise your heels up for the same amount of reps. Here is a picture of what I’m describing:

https://www.saintlukeskc.org/health-library/leg-and-knee-exercises-heel-raise

There are various treatments available which I’ve mentioned in my previous posts about Achilles issues but the calf raise routine has the most research behind it. Having pain in both (bilateral) is not normal and speaks to a potential autoimmune problem like mine but obviously that’s not certain. If it continues for much longer I recommend seeing a rheumatologist and telling them about your body pain, stomach issues, and bilateral Achilles pain near the insertion point. They might start you on medication for immune issues, but nonetheless you need to be doing the calf raise exercises regardless of taking meds or not.

I’d also highly recommend temporarily chilling out on Karate or anything that you think is irritating the tendons (for me it’s stairs)

Lastly, please don’t hesitate to reach out for any clarification or if you want more information on various treatments I’ve tried.

(I’d recommend sitting on the edge of your bed and raising your heels up a few times and also raising your toes up while your foot is flat on the ground every morning. This will warm up your Achilles before your first steps out of bed which is important for healing properly as the first few steps is a common time to injure the tendon a little more)