Why do I feel high/low?

Today went like any other day of school (I'm 15) and after I found some friends around my house and started hanging out I started feeling really euphoric like a high from weed. I quit smoking 6 months ago if that matters. I feel sped up but also slowed down. Sometimes feeling impulsive or having an impaired judgment. This sort of thing happens almost every other day but it only lasts for about 30 minutes - 2 hours so I just p it by but it's 10:00 pm now and this feeling started at around 5pm. Other days I feel depressed for no reason or just apathetic and I've only had 1 or 2 major feeling like that. I'm also feeling more paranoid the more I think about this high feeling....Am I sick? I don't want people to think I'm on a drug or something, please help!