It is easy to tell when a male is aroused. In a female, the vagina gets bigger when she gets aroused to accommodate the penis and she naturally lubricates. Sexual arousal is basically blood flow engorging the tissues in the pelvis making everything swollen and hot. Winter is coming. No, you can't.
Men are often hard-pressed to show their feelings.
Many times they were raised not to show their compassion or love, or their tenderness or sadness. Start with the feelings your man is comfortable with revealing. Even though you can see anxiety in their face, if you ask them, they say they feel fine. I encourage people to help them. Start off with simple feelings like disappointment before something like depression.