In that case don't be concerned with what the psychic said. Remember, its a job, some might have a sixth sense, most want to sell you something. This is a classic scam, for starters most people fear Ouija Boards, second, people fear scorn ex friends/lovers or their new beau curses them. Add these together and your client is scared, then reassure them you can solve their problems if you buy this bag or ring or scarf for a mere 100$ or something.
If you felt nothing before speaking with this psychic, its probably a hoax. If it isn't, you can fix it yourself. Do a cleansing and protection on yourself and home. There are many methods and they work, the cost is just the items you choose to use. Easiest is salt water.
Ouija Boards can be used to contact spirits and demons and it is possible to make a deal with them, but I doubt you did something ap horrible that your ex would consider attempting what the psychic claims. Plus if he doesn't know what he's doing, the demon would go after him.
Anyway, just put it out of your mind, maybe cleanse and protect if you feel like it [it should be done regularly even without an evil presence] and take what people say with a grain of salt.