Achilles tendinitis

hi I have some pain on my left Achilles and I don’t quite know if it is tendinitis. I am running the marathon next weekend and don’t know what to do.

It started last week when I was running and I will say I am not the best at stretching before or after I run I do a little but could probably do more.

Should I rest completely and do some deep stretching and work on loosing up my calves?