If you say no and they keep going until you change your answer to yes, can it still be considered sexual assault/rape?

This question came up during a conversation with my friends, based on one of my past experiences. I was hanging out with my old boyfriend years ago, and he wanted to make out/have sex. I had said no but he kept going regardless, and eventually I changed my mind to yes. One of my friends had said that that is assault because he kept going after I said no, but the other one said it wasn't because I changed my mind. I had honestly never considered what he did as assault; maybe it wasn't okay, but I didn't see it as rape/assault. Thoughts?