I have no idea about the dream meaning, but the change in your medication is probably the trigger.

Medications all effect the body's chemistry. Seeing that your medication is for a serious thing (not simply attention like for me) the change in the dose should create some chaos in the body, likely showing its ugly head in your dreams.

Also, you might want to hold a cross, a bottle of holy water, a wooden stake, or a clove of garlic when you go to sleep, so you take it with you into the dream. If you want, taking a whip would be good too, if you play Castlevainia that is!

All in all, remember that dreams aren't real. I recommend talking with your parents about it and squeezing some soft object if you feel really scared. Hope this helps you out.