What the heck is wrong with me?

Something strange has been happening, i don't know what. I have been having the worst headaches for the last week, it comes sometimes during the day, but mostly at night. I'm becoming very forgetful, I forgot that it was father's day today, if you ask me what I did yesterday, I wouldn't know. my cousin asked me to go over to her house on Saturday night and Monday night, I forgot about asking my parents until My cousin reminded me on Saturday afternoon. My mind keeps going blank, if i'm doing something, 10 minutes later, i'll forget what i'm doing or what the purpose of it is. I feel sad, but have nothing to be sad about, I keep freaking out at everyone over very small matters. I've never been so sweaty, especually in the evenings and night time. I'm been having the worst nightmares for the past week. I get dizzy and everything. What could be wrong with me? Thanks for everyone who answers me. I'll really appreciate it.