I've been sick for almost 5 months with a "cold"..what could this be?

Okay, I have been sick for going on five months now with a could/cough. I went to the doctor when I first started showing symptoms and they said it was just a little cough and told me to gargle with salt water, so I did. The cold never went away so I started taking daytime/night-time cold meds for the drug store for about a week. That didn't seem to help either. So I bought some mucinex and it worked for about a day and then stopped working after that. Finally, I just gave up and went along with the cold for what I thought would be another week or so. Wrong. It has lasted up until now. Suddenly, yesterday I started to feel extremely sick and weak. I started having diarrhea all day and then I had a fever of a 102 last night. I have been feeling light-headed and shaky all day. My mom thinks it's just a 24 hour bug and I should just wait it out. But, with me being sick for so long, I'm worried I may have the flu or maybe even mono. Does anyone have any suggestions as to what this could be or what I should do? Should I see the doctor tomorrow? Any suggestions are appreciated. Thank you