The illness could be from the casting that you did. Sending energy around a person when you do not completely understand what you are doing can effect a person negatively.
I understand you wanted your boyfriend to think of you, miss you, and contact you however you did not say what exactly you did to accomplish this. It is possible that while you did this spell you had negative thoughts towards him because you had not spoken to him in several weeks. Negative thoughts like this can cause a negative reaction in spell work. This is why a clear and focused mind is a must during a casting.
To fix this situation you can cleanse your boyfriend of negative energy by having him take a cleansing bath or by smudging him.