People keep telling you it is not your fault, because it isn’t. It won’t make it go away, no… But you need to acknowledge that you were not the one to abuse. There are many, many ways to say “no”. It doesn’t have to be verbally. They clearly knew that you were not willing, but that did not make them stop. THEY are in the wrong here. Not you.

Also, you were not too stupid, just young, innocent, trusting maybe. The fault should not to lie at your feet, but those who took advantage of what they clearly knew to be wrong.