Hello everyone

. Im an 18 year old male that used to smoke a 1 1/2 to 2 pack s a day for about a year. I quit about 3 or 4 days ago. I've been getting this weird lightheadedness and very little dizziness. I've been deppressed and feel like i'm alone. Also, my heart rate has been lower than it usaully is, and I feel tired even after a full nights rest, and sometimes I have a hard time breathing. I was just wondering if these are symptoms of "Nicotine Withdrawal" or should I be worried about somthing else?