Sex ..

So my fiancé and I have been together for almost six years and we have lived together for 2.5 years. Every since we've moved in together our intimacy level and dropped tremendously. We have sex now on average of once or twice a month. He does work a lot and say that he is tired and I believe him. I work twelve hour shifts at a hospital so I know hard work and being tired. I am almost twelve weeks pregnant and I've had headaches and nausea like crazy. I found a disgusting sock in the floor and no knowing picked it up. Gross. I confronted him about it and he asked me questions about its where a outs whatever. I was I the next room watching tv while he was supposed to be sleeping because he had to work this morning but instead jerking off. I don't know how to feel... I know it's normal to masturbate but masturbate instead of having sex. Idk. I guess I feel like I'm not wanted. I don't think he is seeing anyone else but hey you never know.