The key to understanding your dream is knowing the meaning of the symbols. Here are links to their definition on this site...
hotel
sex
urinating
cheating
phone not working
Dreams are expressions of your feelings about your waking life at the time of the dream. Try to recall what was going on at the time that made you feel demeaned/ashamed, angry, and ultimately needy. Feelings in dreams are never disguised, so how you feel IN the dream is how you feel about its subject in waking life.
First look at the setting of your dream... a hotel, a common symbol of impermanence in relationships. In your dream, you feel close to Mark (sex), but then he urinates on you which makes you feel demeaned and angry. You get back at him by cheating with another. You try to fix it by reaching out by phone but it's broken (communication breakdown) and in the end, you want to make amends.
Your dream reflects a relationship that isn't going well or easily. You seem to want it to work, but you are not getting what you want, which makes you angry. Your anger and frustration make you feel guilty. You "don't want to screw it up." Sound like what's going on in your relationship with Mark recently?
Bottom line, your dream reflects a somewhat disfunctional, even unhealthy relationship. You want intimacy (but he pisses on you) and better communication (but your phone doesn't work.)
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Are you getting what you want from this relationship? Your blackout in the dream would seem to be a metaphor for your lack of awareness about what's really going on with it.
Given that, is he the right guy for you? In your dream, your anger and disappointment are clear. It doesn't sound like a good situation for you... and you don't seem to like what it's doing to you. Just looking at the feelings in the dream, is this how you want to feel in a relationship?
Communication might improve matters... but first you have to repair your communication (phone.) If you can't, you should have your answer.
Hope that helps. Good luck!