Regulus | Cassiopeia
Yes, that must be it. A magical mishap, disrupting your own magic and causing these effects. Perhaps it is some cruel person's idea of a practical joke upon you - which does mean, Regulus dear, that you are not actually a muggle. I'll stand by you on that.
As a temporary measure, you might wear an over-robe on top of the muggle garments? It might help you feel more yourself.
Whatever you think is best. I shall do whatever I can to help you. Potions aren't my speciality but I shall see if I can find any potion books in our library that might be helpful.