>>76245136
What shoes are you running in? Since your race is coming up, you have no time to waste in solving the problem. You have to stretch after running without fail. Calves and hammies especially if your Achilles is bothering you, but just hit all the muscles here >>76244309

I want to know what shoes you run in, on top of that, you may have a QoL improvement available in getting molded insoles. A specialty running store can mold them for you, they might be expensive but the extra arch support could make a big difference.

On top of that, ice the pain area at night. Picrel is a sock with two little silicone cushions on either side of the Achilles, you could wear that at night (not while working out). Gently massages and supports the Achilles