I do agree with dothorey hot and cold is definitely a sign of something. Pisces men should I say are know to be rather inconsistant in a relationship. They are emotional creatures that are very sensitive and can pick up on the slightest vibe from someone else. These vibes are not necessary in their lane but due to the fact that they are receiving them they can not diffirentiate between the real (there problems) and fantasy (someone else's).
I have been married to a piscies for ovev 5 years and dated her all throughout high school, I find her very exciting and sexy. Faithful is her middle name and I trust her to the end. The men on the other hand are very different...they like a variety and will try to get a many different spicy as possible. They don't like to be challenged...but he is messing with your heart, this is not a game he is either in or out, not half and half.