Girls I really need help

I am so confused! I love my fiancé. Actually I don't really know anymore bc of what's going on. I have always said looks don't matter to me, but I something weird is happening and I don't know why. I used to love having sex with him but these past 2 weeks I'm actually been trying to avoid it. Like I will be horny and I will want him but as soon as he kind of gives it back to me I get totally turned off and I don't want to anymore. Please help me understand why this is happening.