I'm so sorry for what you went through, it sounds absolutely awful. Well done you for getting out. Four years later, you're here.
Four years is nothing when it comes to trauma unfortunately. What you're experiencing is horrible, but totally normal.
I wonder if, since you can't escape the trigger (other than hibernating!), you could start a joyful, you-focused ritual that incorporates really good self-care this time every year. So, what I mean is, if you can pick up the basic "start date" of the anniversary, make sure you always book a week off work, or at least a good few days, and be really proactive about planning good happy things, as well as more reflective things. Maybe start your time off with a journalling session, a chat with a loved one who knows your experience (or a session with your therapist), and some kind of release ritual. Write an angry letter to your perpetrator and burn it. Light a candle and cry while it burns, and when it burns out, a deep sigh, open all the windows. Hitting a pillow with a tennis racket. All of the above! Then, once this processing is done, the rest of your time off is spent on nice things - a massage or facial, dinner with your friends, a movie, an at home spa day, lovely food and good rest. Whatever things bring you joy and contentment. Try and imagine what you'd do for a little child who said "this week is always really hard for me" - cherish them with all their favourite things.
I don't know if that appeals to you, but I hope it gives you some ideas. You deserve to reclaim your year, no matter the season/week, and one day it will be easier. By planning something, you'll be more prepared for your triggers and your brain might not feel so hijacked.
Do seek therapy, a lot of people have raved about EMDR for trauma as it's all about processing the memories without talking about them. But perhaps you're a talker and prefer to talk it out and get perspectives.
Keep going. You're way stronger than you know - you're just at the really difficult stage of the journey.