T-shirt collars ride up on neck after top surgery?

Hey all! Long time no see.
So, I'm dealing with a problem that I can't find many other people having online and I thought I would ask you very well informed people.

So, I recently got a double mastectomy, went from I believe C cups to an extremely flat chest.
Since then, I've had quite the trouble with shirts, specifically t-shirts.

They never did this before, but now, the shirt collar rides up on my throat every few minutes. It doesn't seem to matter too much what the size is, large or medium(the 2 sizes of shirts that I regularly wear).
Of course, they also fit looser, but I expected that.
Is this causing the shirts to ride up? Is there any way I can fix this?
Additional, may or may not be relevant details:
I have been on testosterone for 2 years, so could it have something to do with mass increase around my shoulders/neck?
My weight is around 210lbs, and I'm 5'7/5'8.

If anyone knows anything, or could point me to a better place to ask this question I would really appreciate your insight!