I had just arrived from home and found my fiancé lying on the bed with a towel around her waist, and nothing underneath. I first thought she was just sleeping, I came on to her and started touching her. She refused a several times (which was weired), eventually she opened her legs and responded, asked me to switch off the lights which I did, we had sex. When we finished I asked her to sleep under the duvet, and she did, I switched on the light, and I was like she was seeing me for the first time second time, she did not even know she's just had sex, and she was just happy to see me. That means she could have been having sex with anyone and would not know a thing. Has that happened to you? Is it normal?

I have never heard of that. Did you ask her about it. Did she say she didn't know you had just had sex? And Sorry but it sounds like she was either drunk or high. I couldn't tell you which but this is an odd one. If she was neither drunk or high you should have her go see a doctor. Could be a health issue like narcolepsy (spelling) or being that she was under a towel she could have had a shower that was just too hot, walked out by the bed and got a rush of cold air and gone into shock. People are not coherient right after shock and this could explane her not knowing she had had sex. Ask her a few questions about what she was doing before you got home. If she says she was in the shower you probably have your answer. Of course if this happens again I would have her seek medical attention asap.